1,2,4-triazolo[4,3-a]pyridine derivatives and their use as positive allosteric modulators of MGLUR2 receptors

ABSTRACT

The present invention relates to novel triazolo[4,3-a]pyridine derivatives of Formula (I) 
                         
wherein all radicals are as defined in the claims. The compounds according to the invention are positive allosteric modulators of the metabotropic glutamate receptor subtype 2 (“mGluR2”), which are useful for the treatment or prevention of neurological and psychiatric disorders associated with glutamate dysfunction and diseases in which the mGluR2 subtype of metabotropic receptors is involved. The invention is also directed to pharmaceutical compositions comprising such compounds, to processes to prepare such compounds and compositions, and to the use of such compounds for the prevention or treatment of neurological and psychiatric disorders and diseases in which mGluR2 is involved.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the national stage of PCT Application No. PCT/EP2011/069641, filed Nov. 8, 2011, which claims priority from European Patent Application No. 10190327.6, filed Nov. 8, 2010, the entire disclosures of which are hereby incorporated in their entirety.

FIELD OF THE INVENTION

The present invention relates to novel triazolo[4,3-a]pyridine derivatives which are positive allosteric modulators of the metabotropic glutamate receptor subtype 2 (“mGluR2”) and which are useful for the treatment or prevention of neurological and psychiatric disorders associated with glutamate dysfunction and diseases in which the mGluR2 subtype of metabotropic receptors is involved. The invention is also directed to pharmaceutical compositions comprising such compounds, to processes to prepare such compounds and compositions, and to the use of such compounds for the prevention or treatment of neurological and psychiatric disorders and diseases in which mGluR2 is involved.

BACKGROUND OF THE INVENTION

Glutamate is the major amino acid neurotransmitter in the mammalian central nervous system. Glutamate plays a major role in numerous physiological functions, such as learning and memory but also sensory perception, development of synaptic plasticity, motor control, respiration, and regulation of cardiovascular function. Furthermore, glutamate is at the centre of several different neurological and psychiatric diseases, where there is an imbalance in glutamatergic neurotransmission.

Glutamate mediates synaptic neurotransmission through the activation of ionotropic glutamate receptor channels (iGluRs), and the NMDA, AMPA and kainate receptors which are responsible for fast excitatory transmission.

In addition, glutamate activates metabotropic glutamate receptors (mGluRs) which have a more modulatory role that contributes to the fine-tuning of synaptic efficacy.

Glutamate activates the mGluRs through binding to the large extracellular amino-terminal domain of the receptor, herein called the orthosteric binding site. This binding induces a conformational change in the receptor which results in the activation of the G-protein and intracellular signalling pathways.

The mGluR2 subtype is negatively coupled to adenylate cyclase via activation of Gαi-protein, and its activation leads to inhibition of glutamate release in the synapse. In the central nervous system (CNS), mGluR2 receptors are abundant mainly throughout cortex, thalamic regions, accessory olfactory bulb, hippocampus, amygdala, caudate-putamen and nucleus accumbens.

Activating mGluR2 was shown in clinical trials to be efficacious to treat anxiety disorders. In addition, activating mGluR2 in various animal models was shown to be efficacious, thus representing a potential novel therapeutic approach for the treatment of schizophrenia, epilepsy, drug addiction/dependence, Parkinson's disease, pain, sleep disorders and Huntington's disease.

To date, most of the available pharmacological tools targeting mGluRs are orthosteric ligands which activate several members of the family as they are structural analogues of glutamate.

A new avenue for developing selective compounds acting at mGluRs is to identify compounds that act through allosteric mechanisms, modulating the receptor by binding to a site different from the highly conserved orthosteric binding site.

Positive allosteric modulators of mGluRs have emerged recently as novel pharmacological entities offering this attractive alternative. Various compounds have been described as mGluR2 positive allosteric modulators. WO 2009/062676 (Ortho-McNeil-Janssen Pharmaceuticals, Inc. and Addex Pharma S.A.) published on 22 May 2009 discloses imidazo[1,2-a]pyridine derivatives as mGluR2 positive allosteric modulators. WO2010/130424, WO2010/130423 and WO2010/130422, published on 18 Nov. 2010, disclose 1,2,4-triazolo[4,3-a]pyridine derivatives as mGluR2 positive allosteric modulators.

It was demonstrated that such compounds do not activate the receptor by themselves. Rather, they enable the receptor to produce a maximal response to a concentration of glutamate, which by itself induces a minimal response. Mutational analysis has demonstrated unequivocally that the binding of mGluR2 positive allosteric modulators does not occur at the orthosteric site, but instead at an allosteric site situated within the seven transmembrane region of the receptor.

Animal data suggest that positive allosteric modulators of mGluR2 have effects in anxiety and psychosis models similar to those obtained with orthosteric agonists. Allosteric modulators of mGluR2 were shown to be active in fear-potentiated startle, and in stress-induced hyperthermia models of anxiety. Furthermore, such compounds were shown to be active in reversal of ketamine- or amphetamine-induced hyperlocomotion, and in reversal of amphetamine-induced disruption of prepulse inhibition of the acoustic startle effect models of schizophrenia.

Recent animal studies further reveal that the selective positive allosteric modulator of metabotropic glutamate receptor subtype 2 biphenyl-indanone (BINA) blocks a hallucinogenic drug model of psychosis, supporting the strategy of targeting mGluR2 receptors for treating glutamatergic dysfunction in schizophrenia.

Positive allosteric modulators enable potentiation of the glutamate response, but they have also been shown to potentiate the response to orthosteric mGluR2 agonists such as LY379268 or DCG-IV. These data provide evidence for yet another novel therapeutic approach to treat the above mentioned neurological and psychiatric diseases involving mGluR2, which would use a combination of a positive allosteric modulator of mGluR2 together with an orthosteric agonist of mGluR2.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to compounds that are potent mGluR2PAMs with an advantageous balance of properties.

Accordingly, the present invention relates to compounds having metabotropic glutamate receptor 2 modulator activity, said compounds having the Formula (I)

and the stereochemically isomeric forms thereof, wherein R¹ is selected from the group consisting of C₁₋₆alkyl, (C₃₋₈cycloalkyl)C₁₋₃alkyl, (C₁₋₃alkyloxy)C₁₋₃alkyl and C₁₋₃alkyl substituted with 1, 2 or 3 fluoro substituents; R² is selected from the group consisting of C₁, CF₃, —CN and cyclopropyl; R³ is selected from the group consisting of hydrogen, methyl and CF₃; R⁴ is selected from the group consisting of hydrogen and methyl; or R³ and R⁴ together with the carbon to which they are bound form a cyclopropyl ring or a carbonyl group; L is selected from the group consisting of (L-c), (L-a), (L-b), (L-d), (L-e), (L-f) and (L-g):

wherein R^(5a), R^(5b), R^(5c) and R^(5d) are each independently selected from the group consisting of phenyl; phenyl substituted with 1 or 2 substituents each independently selected from the group consisting of C₁₋₃alkyloxy and halo; pyridinyl; pyridinyl substituted with 1 or 2 substituents each independently selected from the group consisting of C₁₋₃alkyl, C₁₋₃alkyloxy and halo; pyrimidinyl and pyrimidinyl substituted with 1 or 2 substituents each independently selected from the group consisting of C₁₋₃alkyl, C₁₋₃alkyloxy and halo; R^(5e) and R^(5f) are each independently selected from the group consisting of phenyl and phenyl substituted with 1 or 2 substituents each independently selected from the group consisting of C₁₋₃alkyloxy and halo; R^(5g) is selected from the group consisting of C₁₋₃alkyl, phenyl and phenyl optionally substituted with 1 or 2 substituents each independently selected from the group consisting of C₁₋₃alkyloxy and halo; R^(6a), R^(6b), R^(6c), R^(6e), R^(6f) and R^(6g) are each independently selected from the group consisting of hydrogen; fluoro; C₁₋₃alkyl; C₁₋₃alkyl substituted with 1, 2 or 3 fluoro substituents; C₁₋₃alkyloxy; C₁₋₃alkyloxy substituted with 1, 2 or 3 fluoro substituents; and C₃₋₆cycloalkyl; R^(7a), R^(8a), R^(7b), R^(8b), R^(7c), R^(8c), R^(7d), R^(8d), R^(7e), R^(8e), R^(7f) and R^(8f) are each independently selected from the group consisting of hydrogen, fluoro and methyl; R^(9b) is selected from the group consisting of hydrogen, C₁₋₃alkyl and C₃₋₆cycloalkyl; wherein each halo is selected from the group consisting of fluoro, chloro, bromo and iodo; and the pharmaceutically acceptable salts and the solvates thereof.

The present invention also relates to a pharmaceutical composition comprising a therapeutically effective amount of a compound of Formula (I) and a pharmaceutically acceptable carrier or excipient.

Additionally, the invention relates to a compound of Formula (I) for use as a medicament and to a compound of Formula (I) for use as a medicament for the treatment or prevention of neurological and psychiatric disorders in which mGluR2 is involved.

The invention also relates to the use of a compound according to Formula (I) or a pharmaceutical composition according to the invention for the manufacture of a medicament for treating or preventing neurological and psychiatric disorders in which mGluR2 is involved.

Additionally, the invention relates to the use of a compound of Formula (I) in combination with an additional pharmaceutical agent for the manufacture of a medicament for treating or preventing neurological and psychiatric disorders in which mGluR2 is involved.

Furthermore, the invention relates to a process for preparing a pharmaceutical composition according to the invention, characterized in that a pharmaceutically acceptable carrier is intimately mixed with a therapeutically effective amount of a compound of Formula (I).

The invention also relates to a product comprising a compound of Formula (I) and an additional pharmaceutical agent, as a combined preparation for simultaneous, separate or sequential use in the treatment or prevention of neurological or psychiatric disorders and diseases.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to compounds of Formula (I) as defined hereinbefore, stereochemically isomeric forms thereof and pharmaceutically acceptable salts and solvates thereof. The compounds of formula (I) have mGluR2 modulatory activity, and are useful in the treatment or prophylaxis of neurological and psychiatric disorders.

In an embodiment, the invention relates to a compound of formula (I) as previously defined, wherein R¹ is (C₃₋₈cycloalkyl)C₁₋₃alkyl.

In an additional embodiment, R¹ is (cyclopropyl)methyl.

In an additional embodiment, R² is CF₃.

In an additional embodiment, R³ and R⁴ are both hydrogen.

In an additional embodiment L is (L-c), wherein R^(5c) is selected from phenyl optionally substituted with 1 or 2 fluoro substituents; R^(6c) is selected from hydrogen or methyl and R^(7c) and R^(8c) are both hydrogen.

All possible combinations of the above-indicated interesting embodiments are considered to be embraced within the scope of this invention.

Particular compounds may be selected from the group of

-   3-(cyclopropylmethyl)-7-[[(3R)-3-phenyl-4-morpholinyl]methyl]-8-(trifluoromethyl)-1,2,4-triazolo[4,3-a]pyridine, -   3-(cyclopropylmethyl)-7-[[(3S)-3-phenyl-4-morpholinyl]methyl]-8-(trifluoromethyl)-1,2,4-triazolo[4,3-a]pyridine, -   3-(cyclopropylmethyl)-7-{[(3*R)-3-(2-fluorophenyl)-3-methylmorpholin-4-yl]methyl}-8-(trifluoromethyl)[1,2,4]triazolo[4,3-a]pyridine, -   3-(cyclopropylmethyl)-7-{[(3*S)-3-(2-fluorophenyl)-3-methylmorpholin-4-yl]methyl}-8-(trifluoromethyl)[1,2,4]triazolo[4,3-a]pyridine, -   3-(cyclopropylmethyl)-7-{[(3*R)-3-(2,4-difluorophenyl)-3-methylmorpholin-4-yl]methyl}-8-(trifluoromethyl)[1,2,4]triazolo[4,3-a]pyridine     and -   3-(cyclopropylmethyl)-7-{[(3*S)-3-(2,4-difluorophenyl)-3-methylmorpholin-4-yl]methyl}-8-(trifluoromethyl)[1,2,4]triazolo[4,3-a]pyridine.

Included within the scope of this list are stereoisomeric forms, the pharmaceutically acceptable salts and the solvates thereof.

The names of the compounds of the present invention were generated according to the nomenclature rules agreed upon by the Chemical Abstracts Service (CAS) using Advanced Chemical Development, Inc., software (ACD/Name product version 10.01; Build 15494, 1 Dec. 2006) or according to the nomenclature rules agreed upon by the International Union of Pure and Applied Chemistry (IUPAC) using Advanced Chemical Development, Inc., software (ACD/Name product version 10.01.0.14105, October 2006). In case of tautomeric forms, the name of the depicted tautomeric form of the structure was generated. However it should be clear that the other non-depicted tautomeric form is also included within the scope of the present invention.

DEFINITIONS

The notation “C₁₋₃alkyl” or “C₁₋₆alkyl” as used herein alone or as part of another group, defines a saturated, straight or branched, hydrocarbon radical having, unless otherwise stated, from 1 to 3 or 1 to 6 carbon atoms, such as methyl, ethyl, 1-propyl, 1-methylethyl, butyl, 1-methyl-propyl, 2-methyl-1-propyl, 1,1-dimethylethyl, 3-methyl-1-butyl, 1-pentyl, 1-hexyl and the like.

The notation “C₃₋₆cycloalkyl” and “C₃₋₈cycloalkyl” as used herein alone or as part of another group, defines a saturated, cyclic hydrocarbon radical having from 3 to 6 or from 3 to 8 carbon atoms, such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl and cyclooctyl.

The notation “halogen” or “halo” as used herein alone or as part of another group, refers to fluoro, chloro, bromo or iodo, with fluoro or chloro being preferred.

The notation “C₁₋₃alkyl substituted with 1, 2 or 3 fluoro substituents” as used herein alone or as part of another group, defines an alkyl group as defined above, substituted with 1, 2 or 3 fluorine atoms, such as fluoromethyl; difluoromethyl; trifluoromethyl; 2,2,2-trifluoroethyl; 1,1-difluoroethyl; 3,3,3-trifluoropropyl. Particular examples of these groups are trifluoromethyl, 2,2,2-trifluoroethyl and 1,1-difluoroethyl.

Whenever the term “substituted” is used in the present invention, it is meant, unless otherwise is indicated or is clear from the context, to indicate that one or more hydrogens, preferably from 1 to 3 hydrogens, more preferably from 1 to 2 hydrogens, more preferably 1 hydrogen, on the atom or radical indicated in the expression using “substituted” are replaced with a selection from the indicated group, provided that the normal valency is not exceeded, and that the substitution results in a chemically stable compound, i.e. a compound that is sufficiently robust to survive isolation to a useful degree of purity from a reaction mixture, and formulation into a therapeutic agent.

It will be appreciated that some of the compounds of formula (I) and their pharmaceutically acceptable addition salts and solvates thereof may contain one or more centres of chirality and exist as stereoisomeric forms.

Hereinbefore and hereinafter, the term “compound of formula (I)” is meant to include the stereoisomers thereof. The terms “stereoisomers” or “stereochemically isomeric forms” hereinbefore or hereinafter are used interchangeably.

The invention includes all stereoisomers of the compound of Formula (I) either as a pure stereoisomer or as a mixture of two or more stereoisomers. Enantiomers are stereoisomers that are non-superimposable mirror images of each other. A 1:1 mixture of a pair of enantiomers is a racemate or racemic mixture. Diastereomers (or diastereoisomers) are stereoisomers that are not enantiomers, i.e. they are not related as mirror images. If a compound contains a double bond, the substituents may be in the E or the Z configuration. If a compound contains an at least disubstituted non aromatic cyclic group, the substituents may be in the cis or trans configuration. Therefore, the invention includes enantiomers, diastereomers, racemates, E isomers, Z isomers, cis isomers, trans isomers and mixtures thereof.

The absolute configuration is specified according to the Cahn-Ingold-Prelog system. The configuration at an asymmetric atom is specified by either R or S. Resolved compounds whose absolute configuration is not known can be designated by (+) or (−) depending on the direction in which they rotate plane polarized light.

When a specific stereoisomer is identified, this means that said stereoisomer is substantially free, i.e. associated with less than 50%, preferably less than 20%, more preferably less than 10%, even more preferably less than 5%, in particular less than 2% and most preferably less than 1%, of the other isomers. Thus, when a compound of formula (I) is for instance specified as (R), this means that the compound is substantially free of the (S) isomer; when a compound of formula (I) is for instance specified as E, this means that the compound is substantially free of the Z isomer; when a compound of formula (I) is for instance specified as cis, this means that the compound is substantially free of the trans isomer.

For therapeutic use, salts of the compounds of formula (I) are those wherein the counterion is pharmaceutically acceptable. However, salts of acids and bases which are non-pharmaceutically acceptable may also find use, for example, in the preparation or purification of a pharmaceutically acceptable compound. All salts, whether pharmaceutically acceptable or not, are included within the ambit of the present invention.

The pharmaceutically acceptable acid and base addition salts as mentioned hereinabove or hereinafter are meant to comprise the therapeutically active non-toxic acid and base addition salt forms which the compounds of Formula (I) are able to form. The pharmaceutically acceptable acid addition salts can conveniently be obtained by treating the base form with such appropriate acid. Appropriate acids comprise, for example, inorganic acids such as hydrohalic acids, e.g. hydrochloric or hydrobromic acid, sulfuric, nitric, phosphoric and the like acids; or organic acids such as, for example, acetic, propanoic, hydroxyacetic, lactic, pyruvic, oxalic (i.e. ethanedioic), malonic, succinic (i.e. butanedioic acid), maleic, fumaric, malic, tartaric, citric, methanesulfonic, ethanesulfonic, benzenesulfonic, p-toluenesulfonic, cyclamic, salicylic, p-aminosalicylic, pamoic and the like acids. Conversely said salt forms can be converted by treatment with an appropriate base into the free base form.

The compounds of Formula (I) containing an acidic proton may also be converted into their non-toxic metal or amine addition salt forms by treatment with appropriate organic and inorganic bases. Appropriate base salt forms comprise, for example, the ammonium salts, the alkali and earth alkaline metal salts, e.g. the lithium, sodium, potassium, magnesium, calcium salts and the like, salts with organic bases, e.g. primary, secondary and tertiary aliphatic and aromatic amines such as methylamine, ethylamine, propylamine, isopropylamine, the four butylamine isomers, dimethylamine, diethylamine, diethanolamine, dipropylamine, diisopropylamine, di-n-butylamine, pyrrolidine, piperidine, morpholine, trimethylamine, triethylamine, tripropylamine, quinuclidine, pyridine, quinoline and isoquinoline; the benzathine, N-methyl-D-glucamine, hydrabamine salts, and salts with amino acids such as, for example, arginine, lysine and the like. Conversely the salt form can be converted by treatment with acid into the free acid form.

The term solvate comprises the solvent addition forms as well as the salts thereof, which the compounds of formula (I) are able to form. Examples of such solvent addition forms are e.g. hydrates, alcoholates and the like.

Some of the compounds according to formula (I) may also exist in their tautomeric form. Such forms although not explicitly indicated in the above formula are intended to be included within the scope of the present invention.

In the framework of this application, an element, in particular when mentioned in relation to a compound according to Formula (I), comprises all isotopes and isotopic mixtures of this element, either naturally occurring or synthetically produced, either with natural abundance or in an isotopically enriched form. Radiolabelled compounds of Formula (I) may comprise a radioactive isotope selected from the group of ³H, ¹¹C, ¹⁸F, ¹²²I, ¹²³I, ¹²⁵I, ¹³¹I, ⁷⁵Br, ⁷⁶Br, ⁷⁷Br, and ⁸²Br. Preferably, the radioactive isotope is selected from the group of ³H, ¹¹C and ¹⁸F.

Preparation

The compounds according to the invention can generally be prepared by a succession of steps, each of which is known to the skilled person. In particular, the compounds can be prepared according to the following synthesis methods.

The compounds of Formula (I) may be synthesized in the form of racemic mixtures of enantiomers which can be separated from one another following art-known resolution procedures. The racemic compounds of Formula (I) may be converted into the corresponding diastereomeric salt forms by reaction with a suitable chiral acid. Said diastereomeric salt forms are subsequently separated, for example, by selective or fractional crystallization and the enantiomers are liberated therefrom by alkali. An alternative manner of separating the enantiomeric forms of the compounds of Formula (I) involves liquid chromatography using a chiral stationary phase. Said pure stereochemically isomeric forms may also be derived from the corresponding pure stereochemically isomeric forms of the appropriate starting materials, provided that the reaction occurs stereospecifically.

A. Preparation of the Final Compounds Experimental Procedure 1

Final compounds according to Formula (I) can be prepared following art known procedures by cyclization of intermediate compound of Formula (II) in the presence of a halogenating agent such as for example phosphorus (V) oxychloride (POCl₃) or trichloroacetonitrile-triphenylphosphine mixture in a suitable solvent such as for example DCE or CH₃CN stirred under microwave irradiation, for a suitable period of time that allows the completion of the reaction, such as for example 50 min at a temperature between 140-200° C.

Alternatively, final compounds of Formula (I) can be prepared by heating the intermediate compound of Formula (II) for a suitable period of time that allows the completion of the reaction, such as for example 1 h at a temperature between 140-200° C. In reaction scheme (1), all variables are defined as in Formula (I).

Experimental Procedure 2

Final compounds according to Formula (I) can be prepared by art known procedures in analogy to the syntheses described in J. Org. Chem., 1966, 31, 251, or J. Heterocycl. Chem., 1970, 7, 1019, by cyclization of intermediate compounds of Formula (III) under suitable conditions in the presence of a suitable ortho-ester of Formula (IV), wherein R¹ is a suitable substituent as defined for compounds of formula (I), like for example, a methyl group, according to reaction scheme (2). The reaction can be carried out in a suitable solvent such as, for example, xylene. Typically, the mixture can be stirred for 1 to 48 h at a temperature between 100-200° C. In reaction scheme (2), all variables are defined as in Formula (I).

Alternatively, final compounds according to Formula (I) can be prepared by art known procedures in analogy to the synthesis described in Tetrahedron Lett., 2007, 48, 2237-2240 by reaction of intermediate compound of Formula (III) with carboxylic acids of Formula (V) or acid equivalents such as acid halides of Formula (VI) to afford final compounds of Formula (I). The reaction can be carried out using a halogenating agent such as for example trichloroacetonitrile-triphenylphosphine mixture in the presence of a suitable solvent such as for example dichloroethane stirred at a temperature between 100-200° C. for 1 to 48 h or under microwave irradiation for 20 min. In reaction scheme (2), all variables are defined as in Formula (I).

Experimental Procedure 3

Final compounds according to Formula (I) can be prepared by art known procedures, by cyclization of intermediate compounds of Formula (VII) under suitable conditions in the presence of a suitable oxidising agent such as copper (II) chloride in a suitable solvent such as DMF, stirred for 1 to 48 h at a temperature between r.t. and 200° C. In reaction scheme (3), all variables are defined as in Formula (I).

Experimental Procedure 4

Alternatively, final compounds according to Formula (I) can be prepared by reacting an intermediate of Formula (VIII) with an intermediate of Formula (IX) under alkylating conditions that are known by those skilled in the art. This is illustrated in reaction scheme (4) wherein all variables are defined as in mentioned hereabove and X is a group suitable for alkylation reactions such as for example halo, methylsulfonate or p-tolylsulfonate. The reaction may be performed, for example, in the presence of a suitable base such as for example diisopropylethylamine in a suitable reaction solvent such as, for example, DMF for a suitable period of time that allows the completion of the reaction at suitable temperature such as for example 120° C.

Experimental Procedure 5

The final compounds according to Formula (I) wherein the carbon between L and the triazolopyrimidine core is monosubstituted either with R³ or R⁴, hereby represented as (I-a), can be prepared by reacting an intermediate of Formula (X) with an intermediate of Formula (IX) under reductive amination conditions that are known by those skilled in the art. This is illustrated in reaction scheme (5) wherein all variables are defined as in Formula (I). The reaction may be performed, for example, in the presence of sodium triacetoxy borohydride in a suitable reaction-inert solvent such as, for example, 1,2-dichloroethane, at a suitable temperature, for example at temperature between r.t. and 150° C., under either classical heating or microwave irradiation, for a suitable period of time that allows the completion of the reaction.

B. Preparation of the Intermediates Experimental Procedure 6

Intermediate compounds according to Formula (II) can be prepared following conditions that are known to those skilled in the art by reacting an intermediate of Formula (III) with a carboxylic acid of Formula (V) via an amide bond formation reaction in the presence of a suitable coupling reagent. This is illustrated in reaction scheme (6) wherein all variables are defined as in Formula (I).

Alternatively, intermediate compounds according to Formula (II) can be prepared by art known procedures by reacting an intermediate of Formula (III) with a carboxylic acid of Formula (V). The reaction can be carried out using a halogenating agent such as for example a trichloroacetonitrile-triphenylphosphine mixture in the presence of a suitable solvent such as for example dichloroethane stirred at a temperature between 100-200° C. for 1 to 48 h or under microwave irradiation for 20 min. In reaction scheme (6), all variables are defined as in Formula (I).

Alternatively, intermediate compounds according to Formula (II) can be prepared by art known procedures by reacting an intermediate of Formula (III) with an acid halide of formula (VI). The reaction can be carried out using a inert-solvent such as for example DCM in the presence of a base such as for example TEA, for example at r.t. for a suitable period of time that allows completion of the reaction. In reaction scheme (6), all variables are defined as in Formula (I).

Experimental Procedure 7

Intermediate compounds according to Formula (III) can be prepared by reacting an intermediate compound of Formula (XI) with hydrazine according to reaction scheme (7), a reaction that is performed in a suitable reaction-inert solvent, such as, for example, ethanol or THF under thermal conditions such as, for example, heating the reaction mixture for example at 160° C. under microwave irradiation for 20 min or classical thermal heating at 90° C. for 16 h. In reaction scheme (7), all variables are defined as in Formula (I) and halo is chloro, bromo or iodo.

Experimental Procedure 8

Intermediate compounds according to Formula (VII) can be prepared following conditions that are known to those skilled in the art by reacting an intermediate of Formula (III) with an aldehyde of Formula (XII) via imine bond formation reaction. The reaction can be carried out using a protic solvent such as for example EtOH, for example at temperature between r.t. and 150° C. for a suitable period of time that allows completion of the reaction. In reaction scheme (8), all variables are defined as in Formula (I).

Experimental Procedure 9

Intermediate compounds according to Formula (XI) wherein the carbon between L and the triazolopyrimidine core is monosubstituted either with R³ or R⁴, hereby represented as (XI-a), can be prepared by reacting an intermediate of Formula (XIII) with an intermediate of Formula (IX) under reductive amination conditions that are known to those skilled in the art. This is illustrated in reaction scheme (9) wherein all variables are defined as in Formula (I). The reaction may be performed, for example, in the presence of triacetoxy borohydride in a suitable reaction-inert solvent such as, for example, DCE, at a suitable temperature, typically at r.t., for a suitable period of time that allows the completion of the reaction.

Experimental Procedure 10

Intermediate compounds according to Formula (XI) wherein CR³R⁴ form a carbonyl group, hereby represented as (XI-b) can be prepared following conditions that are known to those skilled in the art by reacting an intermediate of Formula (XIII-a) with an amine of formula (IX) via an amide bond formation reaction in the presence of a suitable coupling reagent.

Following steps up to the final compounds can be as sequentially defined in experimental procedures 7, 6 and 1

Experimental Procedure 11

Intermediate compounds according to Formula (XIII) can be prepared by reacting an intermediate of Formula (XIV) under conditions that are known to those skilled in the art. This is illustrated in reaction scheme (11) wherein all variables are defined as mentioned hereabove. The reaction may be performed, for example, by first converting the aryl halide into an aryl metal derivative where the metal may be lithium, magnesium, boron or zinc followed by reaction with the appropriate carbonyl compound. Methods accomplishing these transformations are well known to those skilled in the art and include metal-halogen exchange with a Grignard reagent such as isopropylmagnesium chloride or strong base such as for example BuLi in a suitable reaction inert solvent such as THF, diethyl ether or toluene, preferably THF at a temperature between −78° C. and 40° C., followed by reaction with the carbonyl compound such as for example DMF at a temperature between −78° C. and 100° C.

Experimental Procedure 12

Intermediate compounds according to Formula (X) can be prepared by reacting an intermediate of Formula (XV) under dihydroxylation and oxidative cleavage conditions that are known to those skilled in the art and can be realized for example with oxone, osmium tetroxide. The process may be carried out optionally in a solvent such as 1,4-dioxane, water and generally at temperatures between about −100° C. and about 100° C. A summary of such methods is found in “Comprehensive Organic Transformations”, VCH Publishers, (1989), R. C. Larock, pp. 595-596. This is illustrated in reaction scheme (12) wherein all variables are defined as mentioned hereabove.

Experimental Procedure 13

Intermediate compounds according to Formula (XV) can be prepared by coupling reactions, such as Stille or Suzuki reactions, of an intermediate of Formula (XVI) with a compound of Formula (XVII) under conditions that are known to those skilled in the art. This is illustrated in reaction scheme (13) wherein all variables are defined as mentioned hereabove, wherein M is trialkyltin, boronic acid or boronate ester, and a palladium catalyst. The process may be carried out optionally in a solvent such as 1,4-dioxane, water and generally at temperatures between about r.t. and about 200° C. in the presence of a base.

Experimental Procedure 14

Intermediate compounds according to Formula (XVI) can be prepared following art known procedures by cyclization of an intermediate compound of Formula (XVIII) in the presence of a halogenating agent such as for example phosphorus (V) oxychloride (POCl₃) in a suitable solvent such as, for example, dichloroethane, stirred under microwave irradiation, for a suitable period of time that allows the completion of the reaction, as for example 5 min at a temperature between 140-200° C. In reaction scheme (14), all variables are defined as in Formula (I) and halo is chloro, bromo or iodo.

Experimental Procedure 15

Intermediate compounds according to Formula (XVIII) can be prepared by art known procedures by reaction of a hydrazine intermediate of Formula (XIX) with acid halides of Formula (VI). The reaction can be carried out using an inert-solvent, such as for example DCM, in the presence of a base such as for example triethylamine, for example at r.t. for a suitable period of time that allows completion of the reaction, for example 20 min. In reaction scheme (15), all variables are defined as in Formula (I).

Experimental Procedure 16

Intermediate compounds according to Formula (XIX) can be prepared by reacting an intermediate compound of Formula (XX) with hydrazine according to reaction scheme (16), a reaction that is performed in a suitable reaction-inert solvent, such as, for example, ethanol, THF or 1,4-dioxane under thermal conditions such as, for example, heating the reaction mixture for example at 160° C. under microwave irradiation for 30 min or classical thermal heating at 70° C. for 16 h. In reaction scheme (16), R² is defined as in Formula (I) and halo is chloro, bromo or iodo.

Experimental Procedure 17

Intermediate compounds according to Formula (XX) can be prepared by reacting an intermediate compound of Formula (XXI) with benzyl alcohol according to reaction scheme (17), a reaction that is performed in a suitable reaction-inert solvent, such as, for example, N,N-dimethylformamide in the presence of a suitable base, such as for example sodium hydride at r.t. for a suitable period of time that allows the completion of the reaction, such as for example 1 h. In reaction scheme (17), R² is defined as in Formula (I) and halo is chloro, bromo or iodo.

Experimental Procedure 18

Intermediate compounds of Formula (XXI) wherein R² is trifluoromethyl, hereby named (XXI-a), can be prepared by reacting an intermediate of Formula (XXI) wherein R² is iodine, hereby named (XXI-b), with a suitable trifluoromethylating agent, such as for example fluorosulfonyl(difluoro)acetic acid methyl ester, according to reaction scheme (18). This reaction is performed in a suitable reaction-inert solvent such as, for example, N,N-dimethylformamide in the presence of a suitable coupling agent such as for example, copper(I) iodide, under thermal conditions such as, for example, heating the reaction mixture for example at 160° C. under microwave irradiation for 45 min. In reaction scheme (18), halo is chloro, bromo or iodo.

Experimental Procedure 19

Intermediate compounds of Formula (XXI) wherein R² is cyclopropyl, hereby named (XXI-c), can be prepared by an ortho metallation strategy by reacting an intermediate of Formula (XXII) with a substituted or unsubstituted alkyl or an alkenyl halide (XXIII) in the presence of a suitable base, such as lithium diisopropylamide or butyllithium, according to reaction scheme (19) and following references: a) Tetrahedron 2001, 57(19), 4059-4090 or b) Tetrahedron 2001, 57(21), 4489-4505. This reaction is performed in a suitable reaction-inert solvent such as, for example, THF at low temperature such as, for example −78° C. for a period of time that allows the completion of the reaction such as, for example 2-5 h. In reaction scheme (19), halo may be chloro, bromo or iodo and E represents a cyclopropyl radical. If required, intermediates (XXI-c) may be subjected to further simple functional group interconversion steps following art-known procedures to lead to the desirable final R² group.

Experimental Procedure 20

Intermediate compounds according to Formula (VIII) can be prepared from conversion of the hydroxyl group present in intermediate compound of Formula (XXIV) into a suitable leaving group such as for example halogen or mesylate under suitable conditions that are known to those skilled in the art. The reaction may be performed, for example, by reacting an intermediate compound of Formula (XXIV) with methyl sulfonic acid chloride in the presence of a base such as triethylamine, pyridine or halogenating reagens such as for example P(O)Br₃ in a suitable reaction-inert solvent such as, for example, DCM or DMF or mixtures of both, at a suitable temperature, typically at room temperature, for a suitable period of time that allows the completion of the reaction.

Experimental Procedure 21

Intermediate compounds according to Formula (XXIV) wherein the carbon between OH and the triazolopyrimidine core is monosubstituted either with R³ or R⁴, hereby represented as (XXIV-a) can be prepared by reacting an intermediate of Formula (X) under conditions that are known to those skilled in the art. This is illustrated in reaction scheme (21) wherein all variables are defined as mentioned hereabove. The reaction may be performed, for example, by reacting intermediate of Formula (XVII) with a reductive reagent such as for example sodium borohydride in a suitable solvent such as for example methanol. The reaction may be performed at a suitable temperature, typically room temperature, for a suitable period of time that allows the completion of the reaction. This is illustrated in reaction scheme (21) wherein all variables are defined as mentioned hereabove

Experimental Procedure 22

Alternatively, intermediate compounds of Formula (XVI) can be prepared following art known procedures by cyclization of intermediate compound of Formula (XXV) under heating for a suitable period of time that allows the completion of the reaction, as for example 1 h at a temperature between 140-200° C. In reaction scheme (22), all variables are defined as in Formula (I) and halo is chloro, bromo or iodo.

Experimental Procedure 23

Intermediate compounds according to Formula (XXV) can be prepared by art known procedures by reaction of intermediate compounds of Formula (XXVI) with acid halides of Formula (VI). The reaction can be carried out using an inert-solvent such as for example DCM in the presence of a base such as for example triethylamine, for example at r.t. for a suitable period of time that allows completion of the reaction, for example 20 min. In reaction scheme (23), all variables are defined as in Formula (I) and halo is chloro, bromo or iodo.

Experimental Procedure 24

Intermediate compounds according to Formula (XXVI) can be prepared by reacting an intermediate compound of Formula (XXVII) with hydrazine according to reaction scheme (24), a reaction that is performed in a suitable reaction-inert solvent, such as, for example, ethanol, THF or 1,4-dioxane under thermal conditions such as, for example, heating the reaction mixture for example at 160° C. under microwave irradiation for 30 min or classical thermal heating at 70° C. for 16 h. In reaction scheme (24), R² is defined as in Formula (I) and halo is chloro, bromo or iodo.

Experimental Procedure 25

Intermediate compounds of Formula (IX) can be prepared by deprotection of the nitrogen atom in an intermediate compound of formula (XXVIII), wherein PG represents a suitable protecting group for the nitrogen atom, such as for example tert-butoxycarbonyl, ethoxycarbonyl, benzyloxycarbonyl, benzyl and methyl, according to reaction scheme (25) applying art known procedures. For example, when PG represents benzyl, then the deprotection reaction may be performed in a suitable reaction inert solvent, such as for example an alcohol, i.e. methanol, and 1,4-cyclohexadiene, in the presence of a suitable catalyst, such as for example palladium on charcoal, at a moderately high temperature such as, for example, 100° C. in a sealed vessel. Alternatively, when PG represents an alkyloxycarbonyl group, the deprotection reaction can be performed by reaction with a suitable acid, such as for example hydrochloric acid, in a suitable reaction-inert solvent, such as for example 1,4-dioxane at a moderately high temperature, such as for example reflux temperature. In reaction scheme (25), all variables are defined as in formula (I).

The starting materials according to Formulae (IV), (V), (VI), (IX), (XII), (XVII) or (XXVIII) are compounds that are either commercially available or may be prepared according to conventional reaction procedures generally known to those skilled in the art. For example, compounds of formula (IX), such as compounds with CAS numbers CAS 1132928-65-4 and CAS 198015-96-2 are known in the art.

In order to obtain the HCl salts forms of the compounds, several procedures known to those skilled in the art can be used, unless otherwise stated. In a typical procedure, for example, the free base can be dissolved in DIPE or Et₂O and subsequently, a 6N HCl solution in 2-propanol or a 1 N HCl solution in Et₂O can be added dropwise. The mixture typically is stirred for 10 min after which the product can be filtered off. The HCl salt is usually dried in vacuo.

It will be appreciated by those skilled in the art that in the processes described above the functional groups of intermediate compounds may need to be blocked by protecting groups. In case the functional groups of intermediate compounds were blocked by protecting groups, they can be deprotected after a reaction step.

Pharmacology

The compounds provided in this invention are positive allosteric modulators (PAMs) of metabotropic glutamate receptors, in particular they are positive allosteric modulators of mGluR2. The compounds of the present invention do not appear to bind to the glutamate recognition site, the orthosteric ligand site, but instead to an allosteric site within the seven transmembrane region of the receptor. In the presence of glutamate or an agonist of mGluR2, the compounds of this invention increase the mGluR2 response. The compounds provided in this invention are expected to have their effect at mGluR2 by virtue of their ability to increase the response of such receptors to glutamate or mGluR2 agonists, enhancing the response of the receptor.

As used herein, the term “treatment” is intended to refer to all processes, wherein there may be a slowing, interrupting, arresting or stopping of the progression of a disease, but does not necessarily indicate a total elimination of all symptoms.

Hence, the present invention relates to a compound according to the general Formula (I), the stereoisomeric forms thereof and the pharmaceutically acceptable acid or base addition salts and the solvates thereof, for use as a medicament.

The invention also relates to the use of a compound according to the general Formula (I), the stereoisomeric forms thereof and the pharmaceutically acceptable acid or base addition salts and the solvates thereof, or a pharmaceutical composition according to the invention for the manufacture of a medicament.

The invention also relates to a compound according to the general Formula (I), the stereoisomeric forms thereof and the pharmaceutically acceptable acid or base addition salts and the solvates thereof, or a pharmaceutical composition according to the invention for use in the treatment or prevention of, in particular treatment of, a condition in a mammal, including a human, the treatment or prevention of which is affected or facilitated by the neuromodulatory effect of allosteric modulators of mGluR2, in particular positive allosteric modulators thereof.

The present invention also relates to the use of a compound according to the general Formula (I), the stereoisomeric forms thereof and the pharmaceutically acceptable acid or base addition salts and the solvates thereof, or a pharmaceutical composition according to the invention for the manufacture of a medicament for the treatment or prevention of, in particular treatment of, a condition in a mammal, including a human, the treatment or prevention of which is affected or facilitated by the neuromodulatory effect of allosteric modulators of mGluR2, in particular positive allosteric modulators thereof.

The present invention also relates to a compound according to the general Formula (I), the stereoisomeric forms thereof and the pharmaceutically acceptable acid or base addition salts and the solvates thereof, or a pharmaceutical composition according to the invention for use in the treatment, prevention, amelioration, control or reduction of the risk of various neurological and psychiatric disorders associated with glutamate dysfunction in a mammal, including a human, the treatment or prevention of which is affected or facilitated by the neuromodulatory effect of positive allosteric modulators of mGluR2.

Also, the present invention relates to the use of a compound according to the general Formula (I), the stereoisomeric forms thereof and the pharmaceutically acceptable acid or base addition salts and the solvates thereof, or a pharmaceutical composition according to the invention for the manufacture of a medicament for treating, preventing, ameliorating, controlling or reducing the risk of various neurological and psychiatric disorders associated with glutamate dysfunction in a mammal, including a human, the treatment or prevention of which is affected or facilitated by the neuromodulatory effect of positive allosteric modulators of mGluR2.

In particular, the neurological and psychiatric disorders associated with glutamate dysfunction, include one or more of the following conditions or diseases: acute neurological and psychiatric disorders such as, for example, cerebral deficits subsequent to cardiac bypass surgery and grafting, stroke, cerebral ischemia, spinal cord trauma, head trauma, perinatal hypoxia, cardiac arrest, hypoglycemic neuronal damage, dementia (including AIDS-induced dementia), Alzheimer's disease, Huntington's Chorea, amyotrophic lateral sclerosis, ocular damage, retinopathy, cognitive disorders, idiopathic and drug-induced Parkinson's disease, muscular spasms and disorders associated with muscular spasticity including tremors, epilepsy, convulsions, migraine (including migraine headache), urinary incontinence, substance dependence/abuse, substance withdrawal (including substances such as, for example, opiates, nicotine, tobacco products, alcohol, benzodiazepines, cocaine, sedatives, hypnotics, etc.), psychosis, schizophrenia, anxiety (including generalized anxiety disorder, panic disorder, and obsessive compulsive disorder), mood disorders (including depression, major depressive disorder, treatment resistant depression, mania, bipolar disorders, such as bipolar mania), posttraumatic stress disorder, trigeminal neuralgia, hearing loss, tinnitus, macular degeneration of the eye, emesis, brain edema, pain (including acute and chronic states, severe pain, intractable pain, neuropathic pain, and post-traumatic pain), tardive dyskinesia, sleep disorders (including narcolepsy), attention deficit/hyperactivity disorder, and conduct disorder.

In particular, the condition or disease is a central nervous system disorder selected from the group of anxiety disorders, psychotic disorders, personality disorders, substance-related disorders, eating disorders, mood disorders, migraine, epilepsy or convulsive disorders, childhood disorders, cognitive disorders, neurodegeneration, neurotoxicity and ischemia.

Preferably, the central nervous system disorder is an anxiety disorder, selected from the group of agoraphobia, generalized anxiety disorder (GAD), mixed anxiety and depression, obsessive-compulsive disorder (OCD), panic disorder, posttraumatic stress disorder (PTSD), social phobia and other phobias.

Preferably, the central nervous system disorder is a psychotic disorder selected from the group of schizophrenia, delusional disorder, schizoaffective disorder, schizophreniform disorder and substance-induced psychotic disorder.

Preferably, the central nervous system disorder is a personality disorder selected from the group of obsessive-compulsive personality disorder and schizoid, schizotypal disorder.

Preferably, the central nervous system disorder is a substance abuse or substance-related disorder selected from the group of alcohol abuse, alcohol dependence, alcohol withdrawal, alcohol withdrawal delirium, alcohol-induced psychotic disorder, amphetamine dependence, amphetamine withdrawal, cocaine dependence, cocaine withdrawal, nicotine dependence, nicotine withdrawal, opioid dependence and opioid withdrawal.

Preferably, the central nervous system disorder is an eating disorder selected from the group of anorexia nervosa and bulimia nervosa.

Preferably, the central nervous system disorder is a mood disorder selected from the group of bipolar disorders (I & II), cyclothymic disorder, depression, dysthymic disorder, major depressive disorder, treatment resistant depression, bipolar depression, and substance-induced mood disorder.

Preferably, the central nervous system disorder is migraine.

Preferably, the central nervous system disorder is selected from the group of schizophrenia, behavioral and psychological symptoms of dementia, major depressive disorder, treatment resistant depression, bipolar depression, anxiety, depression, generalised anxiety disorder, post-traumatic stress disorder, bipolar mania, epilepsy, attention-deficit/hyperactivity disorder, substance abuse and mixed anxiety and depression.

Preferably, the central nervous system disorder is epilepsy or a convulsive disorder selected from the group of generalized nonconvulsive epilepsy, generalized convulsive epilepsy, petit mal status epilepticus, grand mal status epilepticus, partial epilepsy with or without impairment of consciousness, infantile spasms, epilepsy partialis continua, and other forms of epilepsy.

Preferably, the central nervous system disorder is attention-deficit/hyperactivity disorder.

Preferably, the central nervous system disorder is a cognitive disorder selected from the group of delirium, substance-induced persisting delirium, dementia, dementia due to HIV disease, dementia due to Huntington's disease, dementia due to Parkinson's disease, dementia of the Alzheimer's type, behavioral and psychological symptoms of dementia, substance-induced persisting dementia and mild cognitive impairment.

Of the disorders mentioned above, the treatment of psychosis, schizophrenia, behavioral and psychological symptoms of dementia, major depressive disorder, treatment resistant depression, bipolar depression, anxiety, depression, generalised anxiety disorder, post-traumatic stress disorder, bipolar mania, substance abuse and mixed anxiety and depression, are or particular importance.

Of the disorders mentioned above, the treatment of anxiety, schizophrenia, migraine, depression, and epilepsy are of particular importance.

At present, the fourth edition of the Diagnostic & Statistical Manual of Mental Disorders (DSM-IV) of the American Psychiatric Association provides a diagnostic tool for the identification of the disorders described herein. The person skilled in the art will recognize that alternative nomenclatures, nosologies, and classification systems for neurological and psychiatric disorders described herein exist, and that these evolve with medical and scientific progresses.

Therefore, the invention also relates to a compound according to the general Formula (I), the stereoisomeric forms thereof and the pharmaceutically acceptable acid or base addition salts and the solvates thereof, for use in the treatment of any one of the diseases mentioned hereinbefore.

The invention also relates to a compound according to the general Formula (I), the stereoisomeric forms thereof and the pharmaceutically acceptable acid or base addition salts and the solvates thereof, for use in treating any one of the diseases mentioned hereinbefore.

The invention also relates to a compound according to the general Formula (I), the stereoisomeric forms thereof and the pharmaceutically acceptable acid or base addition salts and the solvates thereof, for the treatment or prevention, in particular treatment, of any one of the diseases mentioned hereinbefore.

The invention also relates to the use of a compound according to the general Formula (I), the stereoisomeric forms thereof and the pharmaceutically acceptable acid or base addition salts and the solvates thereof, for the manufacture of a medicament for the treatment or prevention of any one of the disease conditions mentioned hereinbefore.

The invention also relates to the use of a compound according to the general Formula (I), the stereoisomeric forms thereof and the pharmaceutically acceptable acid or base addition salts and the solvates thereof, for the manufacture of a medicament for the treatment of any one of the disease conditions mentioned hereinbefore.

The compounds of the present invention can be administered to mammals, preferably humans, for the treatment or prevention of any one of the diseases mentioned hereinbefore.

In view of the utility of the compounds of Formula (I), there is provided a method of treating warm-blooded animals, including humans, suffering from any one of the diseases mentioned hereinbefore, and a method of preventing in warm-blooded animals, including humans, any one of the diseases mentioned hereinbefore. Said methods comprise the administration, i.e. the systemic or topical administration, preferably oral administration, of a therapeutically effective amount of a compound of Formula (I), a stereoisomeric form thereof and a pharmaceutically acceptable addition salt or solvate thereof, to warm-blooded animals, including humans.

Therefore, the invention also relates to a method for the prevention and/or treatment of any one of the diseases mentioned hereinbefore comprising administering a therapeutically effective amount of compound according to the invention to a patient in need thereof.

One skilled in the art will recognize that a therapeutically effective amount of the PAMs of the present invention is the amount sufficient to modulate the activity of the mGluR2 and that this amount varies inter alia, depending on the type of disease, the concentration of the compound in the therapeutic formulation, and the condition of the patient. Generally, an amount of PAM to be administered as a therapeutic agent for treating diseases in which modulation of the mGluR2 is beneficial, such as the disorders described herein, will be determined on a case by case by an attending physician.

Generally, a suitable dose is one that results in a concentration of the PAM at the treatment site in the range of 0.5 nM to 200 μM, and more usually 5 nM to 50 μM. To obtain these treatment concentrations, a patient in need of treatment likely will be administered an effective therapeutic daily amount of about 0.01 mg/kg to about 50 mg/kg body weight, preferably from about 0.01 mg/kg to about 25 mg/kg body weight, more preferably from about 0.01 mg/kg to about 10 mg/kg body weight, more preferably from about 0.01 mg/kg to about 2.5 mg/kg body weight, even more preferably from about 0.05 mg/kg to about 1 mg/kg body weight, more preferably from about 0.1 to about 0.5 mg/kg body weight. The amount of a compound according to the present invention, also referred to here as the active ingredient, which is required to achieve a therapeutically effect will, of course vary on case-by-case basis, vary with the particular compound, the route of administration, the age and condition of the recipient, and the particular disorder or disease being treated. A method of treatment may also include administering the active ingredient on a regimen of between one and four intakes per day. In these methods of treatment the compounds according to the invention are preferably formulated prior to admission. As described herein below, suitable pharmaceutical formulations are prepared by known procedures using well known and readily available ingredients.

Because such positive allosteric modulators of mGluR2, including compounds of Formula (I), enhance the response of mGluR2 to glutamate, it is an advantage that the present methods utilize endogenous glutamate.

Because positive allosteric modulators of mGluR2, including compounds of Formula (I), enhance the response of mGluR2 to agonists, it is understood that the present invention extends to the treatment of neurological and psychiatric disorders associated with glutamate dysfunction by administering an effective amount of a positive allosteric modulator of mGluR2, including compounds of Formula (I), in combination with an mGluR2 agonist. Examples of mGluR2 agonists include, for example, LY-379268; DCG-IV; LY-354740; LY-404039; LY-544344; LY-2140023; LY-181837; LY-389795; LY-446433; LY-450477; talaglumetad; MGS0028; MGS0039; (−)-2-oxa-4-aminobicyclo[3.1.0]hexane-4,6-dicarboxylate; (+)-4-amino-2-sulfonylbicyclo[3.1.0]hexane-4,6-dicarboxylic acid; (+)-2-amino-4-fluorobicyclo-[3.1.0]hexane-2,6-dicarboxylic acid; 1S,2R,5S,6S-2-amino-6-fluoro-4-oxobicyclo-[3.1.0]hexane-2,6-dicarboxylic acid; 1S,2R,4S,5S,6S-2-amino-6-fluoro-4-hydroxybicyclo[3.1.0]hexane-2,6-dicarboxylic acid; 1S,2R,3R,5S,6S-2-amino-3-fluorobicyclo[3.1.0]hexane-2,6-dicarboxylic acid; 1S,2R,3S,5S,6S-2-amino-6-fluoro-3-hydroxybicyclo[3.1.0]hexane-2,6-dicarboxylic acid; (+)-4-amino-2-sulfonylbicyclo[3.1.0]hexane-4,6-dicarboxylic acid; (+)-2-amino-4-fluorobicyclo[3.1.0]hexane-2,6-dicarboxylic acid; 1S,2R,5S,6S-2-amino-6-fluoro-4-oxobicyclo[3.1.0]hexane-2,6-dicarboxylic acid; 1S,2R,4S,5S,6S-2-amino-6-fluoro-4-hydroxybicyclo-[3.1.0]hexane-2,6-dicarboxylic acid; 1S,2R,3R,5S,6S-2-amino-3-fluorobicyclo-[3.1.0]hexane-2,6-dicarboxylic acid; or 1S,2R,3S,5S,6S-2-amino-6-fluoro-3-hydroxybicyclo[3.1.0]hexane-2,6-dicarboxylic acid. More preferable mGluR2 agonists include LY-379268; DCG-IV; LY-354740; LY-404039; LY-544344; or LY-2140023.

The compounds of the present invention may be utilized in combination with one or more other drugs in the treatment, prevention, control, amelioration, or reduction of risk of diseases or conditions for which compounds of Formula (I) or the other drugs may have utility, where the combination of the drugs together are safer or more effective than either drug alone.

Pharmaceutical Compositions

The present invention also provides compositions for preventing or treating diseases in which modulation of the mGluR2 receptor is beneficial, such as the disorders described herein. While it is possible for the active ingredient to be administered alone, it is preferable to present it as a pharmaceutical composition. Accordingly, the present invention also relates to a pharmaceutical composition comprising a pharmaceutically acceptable carrier or diluent and, as active ingredient, a therapeutically effective amount of a compound according to the invention, in particular a compound according to Formula (I), a pharmaceutically acceptable salt thereof, a solvate thereof or a stereochemically isomeric form thereof. The carrier or diluent must be “acceptable” in the sense of being compatible with the other ingredients of the composition and not deleterious to the recipients thereof.

The compounds according to the invention, in particular the compounds according to Formula (I), the pharmaceutically acceptable salts thereof, the solvates and the stereochemically isomeric forms thereof, or any subgroup or combination thereof may be formulated into various pharmaceutical forms for administration purposes. As appropriate compositions there may be cited all compositions usually employed for systemically administering drugs.

The pharmaceutical compositions of this invention may be prepared by any methods well known in the art of pharmacy, for example, using methods such as those described in Gennaro et al. Remington's Pharmaceutical Sciences (18^(th) ed., Mack Publishing Company, 1990, see especially Part 8: Pharmaceutical preparations and their Manufacture). To prepare the pharmaceutical compositions of this invention, a therapeutically effective amount of the particular compound, optionally in salt form, as the active ingredient is combined in intimate admixture with a pharmaceutically acceptable carrier or diluent, which carrier or diluent may take a wide variety of forms depending on the form of preparation desired for administration. These pharmaceutical compositions are desirable in unitary dosage form suitable, in particular, for oral, topical, rectal or percutaneous administration, by parenteral injection or by inhalation. For example, in preparing the compositions in oral dosage form, any of the usual pharmaceutical media may be employed such as, for example, water, glycols, oils, alcohols and the like in the case of oral liquid preparations such as, for example, suspensions, syrups, elixirs, emulsions and solutions; or solid carriers such as, for example, starches, sugars, kaolin, diluents, lubricants, binders, disintegrating agents and the like in the case of powders, pills, capsules and tablets. Because of the ease in administration, oral administration is preferred, and tablets and capsules represent the most advantageous oral dosage unit forms in which case solid pharmaceutical carriers are obviously employed. For parenteral compositions, the carrier will usually comprise sterile water, at least in large part, though other ingredients, for example, surfactants, to aid solubility, may be included. Injectable solutions, for example, may be prepared in which the carrier comprises saline solution, glucose solution or a mixture of saline and glucose solution. Injectable suspensions may also be prepared in which case appropriate liquid carriers, suspending agents and the like may be employed. Also included are solid form preparations that are intended to be converted, shortly before use, to liquid form preparations. In the compositions suitable for percutaneous administration, the carrier optionally comprises a penetration enhancing agent and/or a suitable wetting agent, optionally combined with suitable additives of any nature in minor proportions, which additives do not introduce a significant deleterious effect on the skin. Said additives may facilitate the administration to the skin and/or may be helpful for preparing the desired compositions. These compositions may be administered in various ways, e.g., as a transdermal patch, as a spot-on, as an ointment.

It is especially advantageous to formulate the aforementioned pharmaceutical compositions in unit dosage form for ease of administration and uniformity of dosage. Unit dosage form as used herein refers to physically discrete units suitable as unitary dosages, each unit containing a predetermined quantity of active ingredient calculated to produce the desired therapeutic effect in association with the required pharmaceutical carrier. Examples of such unit dosage forms are tablets (including scored or coated tablets), capsules, pills, powder packets, wafers, suppositories, injectable solutions or suspensions and the like, teaspoonfuls, tablespoonfuls, and segregated multiples thereof.

Since the compounds according to the invention are orally administrable compounds, pharmaceutical compositions comprising aid compounds for oral administration are especially advantageous.

In order to enhance the solubility and/or the stability of the compounds of Formula (I) in pharmaceutical compositions, it can be advantageous to employ α-, β- or γ-cyclodextrins or their derivatives, in particular hydroxyalkyl substituted cyclodextrins, e.g. 2-hydroxypropyl-β-cyclodextrin or sulfobutyl-β-cyclodextrin. Also co-solvents such as alcohols may improve the solubility and/or the stability of the compounds according to the invention in pharmaceutical compositions.

The exact dosage and frequency of administration depends on the particular compound of formula (I) used, the particular condition being treated, the severity of the condition being treated, the age, weight, sex, extent of disorder and general physical condition of the particular patient as well as other medication the individual may be taking, as is well known to those skilled in the art. Furthermore, it is evident that said effective daily amount may be lowered or increased depending on the response of the treated subject and/or depending on the evaluation of the physician prescribing the compounds of the instant invention.

Depending on the mode of administration, the pharmaceutical composition will comprise from 0.05 to 99% by weight, preferably from 0.1 to 70% by weight, more preferably from 0.1 to 50% by weight of the active ingredient, and, from 1 to 99.95% by weight, preferably from 30 to 99.9% by weight, more preferably from 50 to 99.9% by weight of a pharmaceutically acceptable carrier, all percentages being based on the total weight of the composition.

The amount of a compound of Formula (I) that can be combined with a carrier material to produce a single dosage form will vary depending upon the disease treated, the mammalian species, and the particular mode of administration. However, as a general guide, suitable unit doses for the compounds of the present invention can, for example, preferably contain between 0.1 mg to about 1000 mg of the active compound. A preferred unit dose is between 1 mg to about 500 mg. A more preferred unit dose is between 1 mg to about 300 mg. Even more preferred unit dose is between 1 mg to about 100 mg. Such unit doses can be administered more than once a day, for example, 2, 3, 4, 5 or 6 times a day, but preferably 1 or 2 times per day, so that the total dosage for a 70 kg adult is in the range of 0.001 to about 15 mg per kg weight of subject per administration. A preferred dosage is 0.01 to about 1.5 mg per kg weight of subject per administration, and such therapy can extend for a number of weeks or months, and in some cases, years. It will be understood, however, that the specific dose level for any particular patient will depend on a variety of factors including the activity of the specific compound employed; the age, body weight, general health, sex and diet of the individual being treated; the time and route of administration; the rate of excretion; other drugs that have previously been administered; and the severity of the particular disease undergoing therapy, as is well understood by those of skill in the area.

A typical dosage can be one 1 mg to about 100 mg tablet or 1 mg to about 300 mg taken once a day, or, multiple times per day, or one time-release capsule or tablet taken once a day and containing a proportionally higher content of active ingredient. The time-release effect can be obtained by capsule materials that dissolve at different pH values, by capsules that release slowly by osmotic pressure, or by any other known means of controlled release.

It can be necessary to use dosages outside these ranges in some cases as will be apparent to those skilled in the art. Further, it is noted that the clinician or treating physician will know how and when to start, interrupt, adjust, or terminate therapy in conjunction with individual patient response.

As already mentioned, the invention also relates to a pharmaceutical composition comprising the compounds according to the invention and one or more other drugs for use as a medicament or for use in the treatment, prevention, control, amelioration, or reduction of risk of diseases or conditions for which compounds of Formula (I) or the other drugs may have utility. The use of such a composition for the manufacture of a medicament as well as the use of such a composition for the manufacture of a medicament in the treatment, prevention, control, amelioration or reduction of risk of diseases or conditions for which compounds of Formula (I) or the other drugs may have utility are also contemplated. The present invention also relates to a combination of a compound according to the present invention and an mGluR2 orthosteric agonist. The present invention also relates to such a combination for use as a medicine. The present invention also relates to a product comprising (a) a compound according to the present invention, a pharmaceutically acceptable salt thereof or a solvate thereof, and (b) a mGluR2 orthosteric agonist, as a combined preparation for simultaneous, separate or sequential use in the treatment or prevention of a condition in a mammal, including a human, the treatment or prevention of which is affected or facilitated by the neuromodulatory effect of mGluR2 allosteric modulators, in particular positive mGluR2 allosteric modulators. The different drugs of such a combination or product may be combined in a single preparation together with pharmaceutically acceptable carriers or diluents, or they may each be present in a separate preparation together with pharmaceutically acceptable carriers or diluents.

The following examples are intended to illustrate but not to limit the scope of the present invention.

Chemistry

Several methods for preparing the compounds of this invention are illustrated in the following Examples. Unless otherwise noted, all starting materials were obtained from commercial suppliers and used without further purification.

Hereinafter, “CI” means chemical ionisation; “DAD” means diode-array detector; “THF” means tetrahydrofuran; “DIPE” means diisopropylether; “DMF” means N,N-dimethylformamide; “EtOAc” means ethyl acetate; “DCM” means dichloro-methane; “DCE” means dichloroethane; “DIPEA” means N,N-diisopropylethylamine; “l” or “L” means liter; “LRMS” means low-resolution mass spectrometry/spectra; “HPLC” means high performance liquid chromatography; “HRMS” means high-resolution mass spectra/spectrometry; “NH₄Ac” means ammonium acetate; “NH₄OH” means ammonium hydroxide; “NaHCO₃” means sodium hydrogencarbonate; “Et₂O” means diethyl ether; “MgSO₄” means magnesium sulphate; “EtOH” means ethanol; “ES” means electrospray; “Na₂SO₄” means sodium sulphate; “CH₃CN” means acetonitrile; “NaH” means sodium hydride; “MeOH” means methanol; “NH₃” means ammonia; “Na₂S₂O₃” means sodium thiosulphate; “AcOH” means acetic acid; “Et₃N” or “TEA” mean triethylamine; “NH₄Cl” means ammonium chloride; “K₂CO₃” means potassium carbonate; “Pd(PPh₃)₄” means tetrakis(triphenylphosphine)palladium(0); “eq” means equivalent; “RP” means reverse phase; “r.t.” means room temperature; “mp” means melting point; “min” means minutes; “h” means hours; “s” means second(s); “sat.” means saturated.

Microwave assisted reactions were performed in a single-mode reactor: Initiator™ Sixty EXP microwave reactor (Biotage AB), or in a multimode reactor: MicroSYNTH Labstation (Milestone, Inc.).

Thin layer chromatography (TLC) was carried out on silica gel 60 F254 plates (Merck) using reagent grade solvents. Open column chromatography was performed on silica gel, particle size 60 Å, mesh=230-400 (Merck) using standard techniques. Automated flash column chromatography was performed using ready-to-connect cartridges from Merck, on irregular silica gel, particle size 15-40 μm (normal phase disposable flash columns) on a SPOT or LAFLASH system from Armen Instrument.

Intermediate 1 (I-1) 2,4-Dichloro-3-iodo-pyridine (I-1)

To a solution of 2,4-dichloropyridine (5.2 g, 35.14 mmol) and diisopropylamine (3.91 g, 38.65 mmol) in dry THF (40 mL) cooled at −78° C. under a nitrogen atmosphere, was added n-butyllithium (24.16 mL, 38.65 mmol, 1.6 M in hexanes) dropwise. The resulting reaction mixture was stirred at −78° C. for 45 min. and then a solution of iodine (9.81 g, 38.651 mmol) in dry THF (20 mL) was added dropwise. The mixture was stirred at −78° C. for 1 h., allowed to warm to r.t., diluted with EtOAc and quenched with NH₄Cl (aqueous sat. solution) and Na₂S₂O₃ (aqueous sat. solution). The organic layer was separated, washed with NaHCO₃ (aqueous sat. solution), dried (Na₂SO₄) and concentrated in vacuo. The crude product was purified by column chromatography (silica gel; DCM in heptane 0/100 to 20/80). The desired fractions were collected and concentrated in vacuo to yield intermediate compound I-1 (7.8 g, 81%).

Intermediate 2 (I-2) 2,4-Dichloro-3-trifluoromethyl-pyridine (I-2)

To a mixture of compound I-1 (2 g, 7.30 mmol) in DMF (50 mL) were added fluorosulfonyl-difluoro-acetic acid methyl ester [C.A.S. 680-15-9] (1.86 ml, 14.60 mmol) and copper (I) iodide (2.79 g, 14.60 mmol). The reaction mixture was heated in a sealed tube at 100° C. for 5 h. After cooling, the solvent was evaporated in vacuo. The crude product was purified by column chromatography (silica gel, DCM). The desired fractions were collected and concentrated in vacuo to yield intermediate compound I-2 (1.5 g, 95%).

Intermediate 3 (I-3) 4-Benzyloxy-2-chloro-3-trifluoromethyl-pyridine (I-3)

To a suspension of NaH (0.49 g, 12.73 mmol, 60% mineral oil) in DMF (50 mL) cooled at 0° C., was added benzyl alcohol (1.26 mL, 12.2 mmol). The resulting mixture was stirred for 2 min. then; intermediate compound I-2 (2.5 g, 11.57 mmol) was added. The resulting reaction mixture was gradually warmed to r.t. and stirred for 1 h. The reaction mixture was quenched with water and extracted with diethyl ether. The organic layer was separated, dried (Na₂SO₄) and concentrated in vacuo. The crude product was purified by column chromatography (silica gel; DCM in Heptane 0/100 to 100/0). The desired fractions were collected and concentrated in vacuo to yield intermediate compound I-3 (1.1 g, 33%).

Intermediate 4 (I-4) 4-(Benzyloxy)-2-hydrazino-3-(trifluoromethyl)pyridine (I-4)

To a suspension of compound I-3 (1.09 g, 3.79 mmol) in 1,4-dioxane (9 mL), was added hydrazine monohydrate (3.67 mL, 75.78 mmol). The reaction mixture was heated at 160° C. under microwave irradiation for 30 min. After cooling, the resulting solution was concentrated in vacuo. The residue thus obtained was dissolved in DCM and washed with NaHCO₃ (aqueous sat. solution). The organic layer was separated, dried (Na₂SO₄) and concentrated in vacuo to yield intermediate compound I-4 (0.89 g, 83%) as a white solid.

Intermediate 5 (I-5) N′-[4-(Benzyloxy)-3-(trifluoromethyl)pyridin-2-yl]-2-cyclopropylacetohydrazide (I-5)

To a solution of I-4 (0.89 g, 3.14 mmol) in dry DCM (3 mL) was added triethyl amine (0.65 mL, 4.71 mmol) and cyclopropyl-acetyl chloride [C.A.S. 543222-65-5] (0.37 g, 3.14 mmol). The resulting reaction mixture was stirred at 0° C. for 20 min. The resulting mixture was then concentrated in vacuo to yield intermediate compound I-5 (1.1 g, 96%).

Intermediate 6 (I-6) 7-Chloro-3-cyclopropylmethyl-8-trifluoromethyl[1,2,4]triazolo[4,3-a]pyridine (I-6)

I-5 (1.14 g, 1.87 mmol) and phosphorous (V) oxychloride (0.35 g, 3.74 mmol) in CH₃CN (10 mL) were heated at 150° C. under microwave irradiation for 10 min. After cooling, the resulting reaction mixture was diluted with DCM and washed with NaHCO₃ (aqueous sat. solution), dried (Na₂SO₄) and concentrated in vacuo. The crude product was purified by column chromatography (silica gel; 7M solution of NH₃ in MeOH in DCM 0/100 to 20/80). The desired fractions were collected and concentrated in vacuo to yield intermediate compound I-6 (0.261 g, 51%) as a white solid.

Intermediate 7 (I-7) 7-Vinyl-3-cyclopropylmethyl-8-trifluoromethyl[1,2,4]triazolo[4,3-a]pyridine (I-7)

A suspension of I-6 (1.65 g, 5.986 mmol), vinylboronic acid pinacol ester (1.218 ml, 7.183 mmol), Pd(PPh₃)₄ (0.346, 0.3 mmol) and NaHCO₃ (aqueous sat. solution, 12.5 ml) in 1,4-dioxane (64.5 ml) was heated at 150° C. under microwave irradiation for 13 min. After cooling, the resulting reaction mixture was diluted with EtOAc/water and filtered through a pad of diatomaceous earth. The filtrate was washed with water and NaCl (aqueous sat. solution) and extracted with EtOAc. The organic layer was separated, dried (Na₂SO₄) and concentrated in vacuo. The residue was purified again by column chromatography (silica; EtOAc in DCM 0/100 to 40/60). The desired fractions were collected and concentrated in vacuo to yield intermediate I-7 (1.34 g, 83.7%).

Intermediate 8 (I-8) 7-Carboxaldehyde-3-cyclopropylmethyl-8-trifluoromethyl[1,2,4]triazolo[4,3-a]pyridine (I-8)

A solution of I-7 (6.24 g, 21.014 mmol), sodium periodate (13.484 g, 63.041 mmol), osmium tetroxide (2.5% in tert-butanol, 10.873 ml, 0.841 mmol) in water (55 ml) and 1,4-dioxane (221 ml) was stirred at r.t. for 2 h. The resulting reaction mixture was diluted with EtOAc/water and filtered through a pad of diatomaceous earth. The filtrate was extracted with EtOAc. The organic layer was separated, dried (Na₂SO₄) and concentrated in vacuo. The solid residue was washed with Et₂O, filtered and dried in vacuo to yield intermediate I-8 (3.84 g, 67.9%).

Intermediate 9 (I-9) 7-Hydroxymethyl-3-cyclopropylmethyl-8-trifluoromethyl[1,2,4]triazolo[4,3-a]pyridine (I-9)

To a solution of I-8 (1.73 g, 6.426 mmol) in MeOH (58 ml) stirred at 0° C., was added portionwise sodium borohydride (0.243, 6.426 mmol). The resulting mixture was stirred at r.t. for 1 h. The resulting mixture was concentrated in vacuo. The residue was treated with water and NaCl (aqueous sat. solution) and extracted with EtOAc. The organic layer was separated and concentrated in vacuo. The residue was purified by column chromatography (silica; MeOH/NH₃ in DCM 0/100 to 5/95). The desired fractions were collected and concentrated in vacuo to yield intermediate I-9 (1.015 g, 58%) as brown syrup.

Intermediate 10 (I-10) 7-(Methylsulfonyloxy)methyl-3-cyclopropylmethyl-8-trifluoromethyl[1,2,4]triazolo-[4,3-a]pyridine (I-10)

To a solution of I-9 (1.341 g, 9.678 mmol) and Et₃N (0.778 ml, 5.612 mmol) in DCM (42 ml) stirred at 0° C., was added dropwise methylsulfonyl chloride (0.749 ml, 9.678 mmol) and stirred at r.t. for 2 h. The resulting mixture was treated with NaHCO₃ (aqueous sat. solution) and extracted with DCM. The organic layer was separated and concentrated in vacuo to yield intermediate I-10 (2.6 g, 87%).

Intermediate 11 (I-11) 2-Amino-2-(5-bromo-2-fluorophenyl)propanenitrile

1-(5-Bromo-2-fluorophenyl)-1-ethanone ([CAS 198477-89-3], 65 g, 299.5 mmol) and NH₄Cl (32 g, 599 mmol) were dissolved in NH₃ (in MeOH, 600 mL). Trimethylsilyl cyanide ([CAS 7677-24-9], 100 g, 1008.6 mmol) was added to the above mixture on an ice bath. The reaction mixture was stirred for 2 days at 30° C. The mixture was evaporated under reduced pressure. The residue was extracted with CH₂Cl₂ (2×300 mL). The organic layer was collected, dried and evaporated to give the crude product, which was purified by flash column chromatography over silica gel (gradient eluent:ethyl acetate/petrol ether from 1/20 to 1/2). The product fraction was collected and evaporated to give I-11 (60 g, 82%).

Intermediate 12 (I-12) 2-Amino-2-(5-bromo-2-fluorophenyl)propanoic acid hydrochloride

I-11 (60 g, 246.8 mmol) was dissolved in a mixture of HCl/EtOH (600 mL). The mixture was refluxed overnight. The reaction mixture was evaporated to give I-12 (80 g).

Intermediate 13 (I-13) Methyl 2-amino-2-(5-bromo-2-fluorophenyl)propanoate

I-12 (80 g, 268 mmol) was dissolved in HCl/MeOH (1000 mL). The mixture was refluxed for 2 days. The mixture was evaporated to remove MeOH. The mixture was extracted with EtOAc (3×200 mL). The pH of the aqueous layer was neutralized with sat. aq. solution of NaHCO₃ to pH 9. The mixture was extracted with EtOAc (3×200 mL). The organic layer was collected and evaporated to give I-13 (31.42 g, 43%) as a brown oil.

Intermediate 14 (I-14) 2-Amino-2-(5-bromo-2-fluorophenyl)propan-1-ol

I-13 (150 g, 543.26 mmol) was dissolved in dry EtOH (1500 mL). Then NaBH₄ (62.42 g, 1629.78 mmol) was added in small portions to the above mixture. The reaction mixture was refluxed for 3 h. Then the reaction was evaporated to remove most of the EtOH. Then water was added to the above mixture and extracted with EtOAc (3×300 mL). The organic layer was collected and evaporated to give I-14 (116.689 g, 87%) as white solid.

Intermediate 15 5-(5-Bromo-2-fluorophenyl)-5-methylmorpholin-3-one (I-15)

Chloroacetyl chloride ([CAS 79-04-9], 1.28 mL, 16.12 mmol) was added dropwise to a stirred solution of I-14 (4 g, 16.12 mmol) in THF (77 mL) and DIPEA (3.334 mL, 19.35 mmol) at −78° C. The mixture was stirred for 30 min at −78° C. Then potassium tert-butoxide (4.523 g, 40.31 mmol) was added and the mixture was left warming up to RT during 20 min. The crude was stirred and warmed to 50° C. for 2 h. The mixture was diluted with sat. aq. NH₄Cl and extracted with EtOAc. The organic layer was separated, dried (Na₂SO₄), filtered and the solvents evaporated in vacuo. The reaction was repeated to exhaust the starting material. Chloroacetyl chloride (0.192 mL, 2.42 mmol) was added dropwise to a stirred solution of the crude in THF (77 mL) and DIPEA (0.500 mL, 2.90 mmol) at −78° C. The mixture was stirred for 30 min at −78° C. Then potassium tert-butoxide (0.678 g, 6.05 mmol) was added and the mixture was left warming up to RT during 20 min. The crude was stirred and warmed to 50° C. for 2 h. The mixture was diluted with sat. NH₄Cl and extracted with EtOAc. The organic layer was separated, dried (Na₂SO₄), filtered and the solvents evaporated in vacuo. The crude was treated with EtOH/Et₂O to afford I-15 (1.396 g, 30%) as a white solid.

Intermediate 16 5-(2-Fluorophenyl)-5-methylmorpholin-3-one (I-16)

Palladium on carbon (25.53 mg) was added to a solution of I-15 (0.24 g, 0.83 mmol) in MeOH (10 mL) under nitrogen atmosphere. The mixture was hydrogenated (atmospheric pressure) at RT for 3 days. More Pd/C (5.3 mg) was added under nitrogen and the mixture was hydrogenated (atmospheric pressure) at RT for 20 h. The mixture was filtered through diatomaceous earth and the filtrate was evaporated in vacuo to yield I-16 (0.213 g, 88%) as a light brown solid.

An additional batch was obtained by an analogous procedure; Palladium on carbon (148.5 mg, 1.40 mmol) was added to a solution of I-15 (1.396 g, 4.85 mmol) in MeOH (50 mL) under a nitrogen atmosphere. The mixture was hydrogenated (atmospheric pressure) at RT for 18 h, then filtered through diatomaceous earth. The filtrate was evaporated in vacuo to yield I-16 (1.47 g, quant.) as a cream solid. Both batches were combined.

Intermediates 17 (I-17), 17a (I-17a) and 17b (I-17b) 3-(2-Fluorophenyl)-3-methylmorpholine (I-17), (3*R)-3-(2-Fluorophenyl)-3-methylmorpholine (I-17a) and (3*S)-3-(2-Fluorophenyl)-3-methylmorpholine (I-17b)

Borane tetrahydrofuran complex solution ([CAS 14044-65-6] 1.0 M in THF, 22.71 mL, 22.71 mmol) was added to a stirred solution of I-16 (combination of two batches, 1.188 g, 5.68 mmol) in THF (147.19 mL) under nitrogen at RT. The mixture was stirred at 80° C. for 16 h. Then, MeOH (1.15 mL) and HCl (1M in H₂O, 28.39 mL, 28.39 mmol) were added. The mixture was stirred at RT for 1 h. Then, the mixture was basified with 50% NaOH. The mixture was extracted with Et₂O. The organic layer was separated, dried (Na₂SO₄), filtered and the solvent evaporated in vacuo. The crude product was purified by flash column chromatography (silica; MeOH in CH₂Cl₂ 0/100 to 5/95). The desired fractions were collected and concentrated in vacuo. The product was dissolved in Et₂O and converted into the hydrochloric acid salt with 6M HCl in 2-propanol. The salt was filtered and then, treated with aqueous NaOH and extracted with CH₂Cl₂. The organic layer was separated, dried (Na₂SO₄), filtered and the solvent evaporated in vacuo to yield I-17 (0.686 g, 62%) as a colourless oil, which was purified by chiral SFC on CHIRALCEL OD-H 5 μm 250×20 mm; mobile phase 0.3% isopropylamine, 95% CO₂, 5% mixture of heptane/iPrOH 50/50 v/v, yielding I-17a (148 mg, 13%) and I-17b (154 mg, 14%) as yellow oils.

Intermediate 18 (I-18) 1-(5-Bromo-2,4-difluorophenyl)ethanone

A mixture of AlCl₃ (1040 g, 7878.7 mmol) in 1-bromo-2,4-difluorobenzene ([CAS 348-57-2], 600 g, 3108.9 mmol) was stirred for 10 min at 60° C. Acetyl chloride [CAS 75-36-5], 366 g, 4662.4 mmol) was added dropwise in the reaction mixture for 4 h at 60° C. The mixture was stirred an additional 6 h at 95° C. The reaction mixture was cooled to −10° C. Ice (2450 g) was added for 1.5 h. HCl (12 N, 1500 mL) was added and the mixture was stirred for 1 h. EtOAc (9000 mL) was added and the organic layer was washed with water, dried over Na₂SO₄ and filtered. After concentration, the residue was purified by column chromatography over silica gel (eluent: petroleum ether/EtOAc, 50/1) to yield I-18 (300 g, 41%).

Intermediate 19 (I-19) 2-Amino-2-(5-bromo-2,4-difluorophenyl)propanenitrile

A mixture of I-18 (300 g, 1276.5 mmol), trimethylsilyl cyanide [CAS 7677-24-9], 380 g, 3830.2 mmol) and NH₄Cl (205 g, 3831.7 mmol) in NH₃ (4N in MeOH, 3000 mL) was stirred for 108 h at 12° C. The reaction mixture was evaporated in vacuo. DCM (3000 mL) was added and filtered. After concentration, the residue was purified by column chromatography over silica gel (eluent: petroleum ether/EtOAc, 50/1) to yield I-19 (212 g, 64%).

Intermediate 20 (I-20) 2-Amino-2-(5-bromo-2,4-difluorophenyl)propanoic acid

A mixture of I-19 (212 g, 812.2 mmol) and HCl (12 N, 1000 mL) in CH₃CO₂H (1000 mL) was heated to reflux for 72 h. The reaction mixture was evaporated in vacuo. EtOAc (1000 mL) and water (1000 mL) were added and the water layer was washed with EtOAc (1000 mL). The water layer was collected and adjusted to pH 7. EtOAc (1000 mL) was added and the organic layer was dried over Na₂SO₄, filtered and the solvent was evaporated in vacuo to yield I-20 (141 g, 62%).

Intermediate 21 (I-21) Methyl 2-amino-2-(5-bromo-2,4-difluorophenyl)propanoate

A mixture of I-20 (141 g, 432.1 mmol) in HCl (4N in MeOH, 1500 mL) was heated to reflux for 108 h. The reaction mixture was evaporated in vacuo. EtOAc (1000 mL) and water (1000 mL) were added and the water layer was washed with EtOAc (1000 mL).

The water layer was collected and adjusted to pH 7. EtOAc (2000 mL) was added and the organic layer was dried over Na₂SO₄, filtered and the solvent was evaporated in vacuo to yield I-21 (92 g, 78%).

Intermediates 22 (I-22), I-22a (I-22a) and I-22b (I-22b) 2-Amino-2-(5-bromo-2,4-difluorophenyl)propan-1-ol (I-22), (2S)-2-Amino-2-(5-bromo-2,4-difluorophenyl)propan-1-ol (I-22a) and (2R)-2-Amino-2-(5-bromo-2,4-difluoro-phenyl)propan-1-ol (I-22b)

A mixture of I-21 (160 g, 544.2 mmol) and NaBH₄ (41 g, 1078.9 mmol) in EtOH (1500 mL) was stirred for 72 h at 14° C. The reaction mixture was evaporated in vacuo. EtOAc (500 mL) was added and the organic layer was washed with water, dried over Na₂SO₄, filtered and the solvent was evaporated in vacuo to yield crude I-22 (132 g, 91%). To crude I-22 (100 g) was added heptane (around 1.8 L), and the mixture was heated to 110° C. Then the dissolved product was separated by filtration over a warm filter. When the mixture cooled to 60-70° C., the solution was decanted and left cooling further, while stirring, to RT. The off-white precipitated product was filtered and dried in vacuo, to yield 72.4 g of I-22, which was purified by chiral SFC on CHIRALPAK AD-H 5 μm 250×20 mm; mobile phase: 0.3% isopropylamine, 90% CO₂, 10% MeOH, yielding I-22a (33.5 g) and I-22b (35.6 g).

Intermediate 23 (I-23) 5-(5-Bromo-2,4-difluorophenyl)-5-methylmorpholin-3-one

Chloroacetyl chloride ([CAS 79-04-9], 0.599 mL, 7.52 mmol) was added dropwise to a stirred solution of I-22 (2 g, 7.52 mmol, recovered after resolution step using chiral stationary phase) in THF (72.0 mL) and DIPEA (1.554 mL, 9.02 mmol) at −78° C. The mixture was stirred for 30 min at −78° C. Then potassium tert-butoxide (2.109 g, 18.79 mmol) was added and the mixture was left warming up to RT during 20 min. The crude was stirred and warmed to 50° C. for 2 h. The mixture was diluted with sat. aq. NH₄Cl and extracted with EtOAc. The organic layer was separated, dried (Na₂SO₄), filtered and the solvents evaporated in vacuo. The crude was treated with EtOH/Et₂O to afford crude I-23 as a white solid which was triturated with diisopropyl ether to yield I-23 (0.524 g, 23%) as a cream solid.

Intermediate 24 (I-24) 5-(2,4-Difluorophenyl)-5-methylmorpholin-3-one

Pd/C (7.9 mg, 0.074 mmol) was added to a solution of I-23 (101.97 mg, 0.33 mmol) in MeOH (10 mL) under nitrogen atmosphere. The mixture was hydrogenated (atmospheric pressure) at RT for 20 h. More Pd/C (2.31 mg, 0.022 mmol) was added under nitrogen and the mixture was hydrogenated (atmospheric pressure) at RT for 3 days. The mixture was filtered through diatomaceous earth and the filtrate was evaporated in vacuo to yield I-24 (75.6 mg, 76%) as an off-white solid.

Intermediates 25 (I-25), 25a (I-25a) and 25b (I-25b) 3-(2-Fluorophenyl)-3-methylmorpholine (I-25), (3*R)-3-(2-Fluorophenyl)-3-methylmorpholine (I-25a) and (3*S)-3-(2-Fluorphenyl)-3-methylmorpholine (I-25b)

Intermediates I-25, I-25a and I-25b were synthesized following an analogous procedure as that described for I-17/a/b starting from intermediate I-24 (1.413 g, 6.22 mmol). Intermediate I-25 (0.772 g, 57%) was obtained as a colourless oil that was purified by chiral SFC on CHIRALPAK AD-H 5 μm 250×20 mm, mobile phase: 0.3% isopropylamine, 95% CO₂, 5% iPrOH, yielding I-25a (150 mg, 11%) and I-25b (150 mg, 11%) as yellow oils.

Final Products Example 1 3-(Cyclopropylmethyl)-7-[[(3R)-3-phenyl-4-morpholinyl]methyl]-8-(trifluoromethyl)-1,2,4-triazolo[4,3-c]pyridine (E-1)

Sodium triacetoxyborohydride (0.060 g, 0.30 mmol) was added to a stirred solution of I-8 (0.28 g, 1.03 mmol) and (R)-3-phenylmorpholine [(C.A.S. 74572-03-5), 0.461 g, 1.24 mmol] in 1,2-dichloroethane (15.5 mL). The mixture was stirred at 120° C. for 20 minutes under microwave irradiation, then more sodium triacetoxyborohydride (0.294 g, 1.4 mmol) was added and the reaction heated again at the same condition as before. After that more sodium triacetoxyborohydride (0.105 g, 0.5 mmol) was added again and the reaction heated as before. The mixture was then treated with sat. NaHCO₃ and extracted with CH₂Cl₂. The organic layer was separated, dried (Na₂SO₄), filtered and the solvents evaporated in vacuo. The crude product was purified by flash column chromatography (silica; EtOAC in CH₂Cl₂ 0/100 to 40/60). The desired fractions were collected and concentrated in vacuo to give the desired compound 85% pure. The product was then further purified by RP HPLC on (C18 XBridge™ 30×100 5 um). Mobile phase (Gradient from 80% 0.1% NH₄CO₃H/NH₄OH pH 9 solution in Water, 20% CH₃CN to 0% 0.1% NH₄CO₃H/NH₄OH pH 9 solution in Water, 100% CH₃CN), yielding E-1 (0.063 g, 14.5%) as a white solid.

Example 2 3-(Cyclopropylmethyl)-7-[[(3S)-3-phenyl-4-morpholinyl]methyl]-8-(trifluoromethyl)-1,2,4-triazolo[4,3-c]pyridine (E-2)

Example E-2 was synthesized following the same approach described for E-1 starting from intermediate I-8 (0.207 g, 0.77 mmol) and (S)-3-phenylmorpholine (C.A.S. 914299-79-9). Example E-2 (0.025 g, 7.7%) was obtained as colorless sticky solid.

Example 4a 3-(Cyclopropylmethyl)-7-{[(3*R)-3-(2-fluorophenyl)-3-methylmorpholin-4-yl]methyl}-8-(trifluoromethyl)[1,2,4]triazolo[4,3-a]pyridine

A solution of I-10 (60 mg, 0.15 mmol) in CH₃CN (1.5 mL) and then DIPEA (38.63 μL, 0.22 mmol) was added to a stirred mixture of I-17a (32.09 mg, 0.16 mmol) and NaI (2.24 mg, 0.015 mmol) in CH₃CN (1 mL) in a sealed tube and the mixture was stirred at 90° C. for 2 days. The mixture was evaporated in vacuo. The residue was purified by flash column chromatography (silica; 7 M solution of NH₃ in MeOH in CH₂Cl₂ 0/100 to 5/95). The desired fractions were collected and concentrated in vacuo to yield 27.3 mg of crude E-4a which was purified by RP HPLC on C18 XBridge 19×100, 5 um; mobile phase: gradient from 80% 0.1% NH₄CO₃H/NH₄OH pH 9 solution in water, 20% CH₃CN to 0% 0.1% NH₄CO₃H/NH₄OH pH 9 solution in water, 100% CH₃CN), yielding E-4a (12 mg, 18%) as a white solid.

Example 4b 3-(Cyclopropylmethyl)-7-{[(3*S)-3-(2-fluorophenyl)-3-methylmorpholin-4-yl]methyl}-8-(trifluoromethyl)[1,2,4]triazolo[4,3-a]pyridine

Example E-4-b was synthesized following the same approach described for E-4a starting from intermediate I-10 (60 mg, 0.15 mmol) and intermediate I-17b (32.09 mg, 0.16 mmol). Example E-4-b (19.67 mg, 29%) was obtained as a sticky white solid.

Example 5a 3-(Cyclopropylmethyl)-7-{[(3*R)-3-(2,4-difluorophenyl)-3-methylmorpholin-4-yl]methyl}-8-(trifluoromethyl)[1,2,4]triazolo[4,3-a]pyridine

Example E-5a was synthesized following an analogous procedure to that described for E-4a starting from intermediate I-10 (60 mg, 0.15 mmol) and intermediate I-25a (35.05 mg, 0.16 mmol). Example E-5a (11.45 mg, 16%) was obtained as a white solid.

Example 5b 3-(Cyclopropylmethyl)-7-{[(3*S)-3-(2,4-difluorophenyl)-3-methylmorpholin-4-yl]methyl}-8-(trifluoromethyl)[1,2,4]triazolo[4,3-a]pyridine

Example E-5b was synthesized following an analogous procedure to that described for E-4a starting from intermediate I-10 (60 mg, 0.15 mmol) and intermediate I-25b (35.05 mg, 0.16 mmol). Example E-5a (9.72 mg, 14%) was obtained as a white solid.

Table 1 below lists additional compounds of Formula (I).

TABLE 1 Example compounds according to Formula (I).

Co. Exp Stereo- no. no. R¹ R² - - - -[CH(R)_(m)]_(n)—L chem. 1 E1

- - - -CF₃

R 2 E2

- - - -CF₃

S 3 E1

- - - -CF₃

4 E1

- - - -CF₃

4a E4a

- - - -CF₃

*R 4b E4b

- - - -CF₃

*S 5 E1

- - - -CF₃

5a E5a

- - - -CF₃

*R 5b E5b

- - - -CF₃

*S Additional compounds 3, 4 and 5, can be prepared by analogy to the above examples (Exp. No.). The stereochemical configuration for some compounds has been designated *R or *S when their absolute stereochemistry is undetermined although the compound itself has been isolated as a single stereoisomer and is enantiomerically pure.

C. Analytical Part

Melting Points

Values are peak values, and are obtained with experimental uncertainties that are commonly associated with this analytical method. For a number of compounds, melting points were determined in open capillary tubes either on a Mettler FP62 or on a Mettler FP81HT-FP90 apparatus. Melting points were measured with a temperature gradient of 10° C./min. Maximum temperature was 300° C. The melting point was read from a digital display.

Optical Rotation

Optical rotations were measured on a Perkin-Elmer 341 polarimeter with a sodium lamp and reported as follows: [α]° (λ, c g/100 ml, solvent, T ° C.). [α]_(λhu T)=(100α)/(l×c): where l is the path length in dm and c is the concentration in g/100 ml for a sample at a temperature T (° C.) and a wavelength λ (in nm). If the wavelength of light used is 589 nm (the sodium D line), then the symbol D might be used instead. The sign of the rotation (+ or −) should always be given. When using this equation the concentration and solvent are always provided in parentheses after the rotation. The rotation is reported using degrees and no units of concentration are given (it is assumed to be g/100 ml).

LCMS

For LCMS characterization of the compounds of the present invention, the following methods were used.

General Procedure A (for Waters MS Instruments (Acquity SOD))

The UPLC (Ultra Performance Liquid Chromatography) measurement was performed using an Acquity UPLC (Waters) system comprising a sampler organizer, a binary pump with degasser, a four column's oven, a DAD and a column as specified in the respective methods below. Column flow was used without split to the MS detector. The MS detector was configured with an ESCI dual ionization source (ES combined with atmospheric pressure CI). Nitrogen was used as the nebulizer gas. The source temperature was maintained at 140° C. Data acquisition was performed with MassLynx-Openlynx software.

Method 1

In addition to the general procedure A: Reversed phase UPLC was carried out on a BEH-C18 column (1.7 μm, 2.1×50 mm) from Waters, with a flow rate of 1.0 ml/min, at 50° C. without split to the MS detector. The gradient conditions used are: 95% A (0.5 g/l ammonium acetate solution+5% acetonitrile), 5% B (acetonitrile), to 40% A, 60% B in 3.8 minutes, to 5% A, 95% B in 4.6 minutes, kept till 5.0 minutes. Injection volume 2 μl. Low-resolution mass spectra (single quadrupole, SQD detector) were acquired by scanning from 100 to 1000 in 0.1 seconds using an inter-channel delay of 0.08 second. The capillary needle voltage was 3 kV. The cone voltage was 25 V for positive ionization mode and 30 V for negative ionization mode.

Method 2:

same gradient as method 2; column used: RRHD Eclipse Plus-C18 (1.8 μm, 2.1×50 mm) from Agilent.

The results of the analytical measurements are shown in table 2.

TABLE 2 Physico-chemical data for some compounds, retention time (R_(t)) in min, [M + H]⁺ peak (protonated molecule), LCMS method and mp (melting point in ° C.). Mp R_(t) LCMS Co. No. (° C.) [MH⁺] (min) Method Optical Rotation 1  69.2 417 2.67 1 +62.9° (589 nm, c 0.54 w/v %, DMF, 20° C.) 2  n.d. 417 2.66 1 −52.7° (589 nm, c 0.55 w/v %, DMF, 20° C.) 4a n.d. 449 3.13 2 −169.6° (589 nm, c 0.85 w/v %, MeOH, 20° C.) 4b n.d. 449 3.13 2 +81.6 (589 nm, c 0.54 w/v %, MeOH, 20° C.) 5a n.d. 467 3.21 2 +48.0 (589 nm, c 0.83 w/v %, MeOH, 20° C.) 5b n.d. 467 3.21 2 −128.2 (589 nm, c 0.67 w/v %, MeOH, 20° C.) (nd = not determined). Nuclear Magnetic Resonance (NMR)

For a number of compounds, ¹H NMR spectra were recorded either on a Bruker DPX-400 or on a Bruker AV-500 spectrometer with standard pulse sequences, operating at 400 MHz and 500 MHz, respectively. Chemical shifts (6) are reported in parts per million (ppm) downfield from tetramethylsilane (TMS), which was used as internal standard.

Co.No. 1

¹H NMR (500 MHz, CDCl₃) δ ppm 0.28-0.42 (m, 2H), 0.57-0.71 (m, 2H), 1.12-1.23 (m, 1H), 2.46 (td, J=11.8, 3.0 Hz, 1H), 2.63 (br. d, J=11.8 Hz, 1H), 3.09 (d, J=6.6 Hz, 2H), 3.47-3.59 (m, 3H), 3.62-3.76 (m, 2H), 3.77-3.86 (m, 1H), 3.89 (br. d, J=11.3 Hz, 1H), 7.28-7.34 (m, 1H), 7.34-7.39 (m, 2H), 7.40 (d, J=7.2 Hz, 1H), 7.45 (br. d, J=7.2 Hz, 2H), 8.06 (d, J=7.2 Hz, 1H)

Co.No. 2

¹H NMR (400 MHz, CDCl₃) δ ppm 0.27-0.42 (m, 2H), 0.56-0.71 (m, 2H), 1.12-1.23 (m, 1H), 2.46 (td, J=11.6, 2.9 Hz, 1H), 2.63 (br. d, J=11.8 Hz, 1H), 3.09 (d, J=6.7 Hz, 2H), 3.47-3.58 (m, 3H), 3.62-3.76 (m, 2H), 3.78-3.86 (m, 1H), 3.89 (br. d, J=11.3 Hz, 1H), 7.28-7.34 (m, 1H), 7.34-7.39 (m, 2H), 7.40 (d, J=7.2 Hz, 1H), 7.45 (br. d, J=7.4 Hz, 2H), 8.06 (d, J=7.4 Hz, 1H).

D. Pharmacological Examples

[³⁵S]GTPγS Binding Assay

The compounds provided in the present invention are positive allosteric modulators of mGluR2. These compounds appear to potentiate glutamate responses by binding to an allosteric site other than the glutamate binding site. The response of mGluR2 to a concentration of glutamate is increased when compounds of Formula (I) are present. Compounds of Formula (I) are expected to have their effect substantially at mGluR2 by virtue of their ability to enhance the function of the receptor. The effects of positive allosteric modulators tested at mGluR2 using the [³⁵S]GTPγS binding assay method described below and which is suitable for the identification of such compounds, and more particularly the compounds according to Formula (I), are shown in Table 3.

[³⁵S]GTPγS Binding Assay

The [³⁵S]GTPγS binding assay is a functional membrane-based assay used to study G-protein coupled receptor (GPCR) function whereby incorporation of a non-hydrolysable form of GTP, [³⁵S]GTPγS (guanosine 5′-triphosphate, labelled with gamma-emitting ³⁵S), is measured. The G-protein a subunit catalyzes the exchange of guanosine 5′-diphosphate (GDP) by guanosine triphosphate (GTP) and on activation of the GPCR by an agonist, [³⁵S]GTPγS, becomes incorporated and cannot be cleaved to continue the exchange cycle (Harper (1998) Current Protocols in Pharmacology 2.6.1-10, John Wiley & Sons, Inc.). The amount of radioactive [³⁵S]GTPγS incorporation is a direct measure of the activity of the G-protein and hence the activity of the agonist can be determined mGluR2 receptors are shown to be preferentially coupled to Gαi-protein, a preferential coupling for this method, and hence it is widely used to study receptor activation of mGluR2 receptors both in recombinant cell lines and in tissues. Here we describe the use of the [³⁵S]GTPγS binding assay using membranes from cells transfected with the human mGluR2 receptor and adapted from Schaffhauser et al. ((2003) Molecular Pharmacology 4:798-810) for the detection of the positive allosteric modulation (PAM) properties of the compounds of this invention.

Membrane Preparation

CHO-cells were cultured to pre-confluence and stimulated with 5 mM butyrate for 24 h. Cells were then collected by scraping in PBS and cell suspension was centrifuged (10 min at 4000 RPM in benchtop centrifuge). Supernatant was discarded and pellet gently resuspended in 50 mM Tris-HCl, pH 7.4 by mixing with a vortex and pipetting up and down. The suspension was centrifuged at 16,000 RPM (Sorvall RC-5C plus rotor SS-34) for 10 minutes and the supernatant discarded. The pellet was homogenized in 5 mM Tris-HCl, pH 7.4 using an ultra-turrax homogenizer and centrifuged again (18,000 RPM, 20 min, 4° C.). The final pellet was resuspended in 50 mM Tris-HCl, pH 7.4 and stored at −80° C. in appropriate aliquots before use. Protein concentration was determined by the Bradford method (Bio-Rad, USA) with bovine serum albumin as standard.

[³⁵S]GTPγS Binding Assay

Measurement of mGluR2 positive allosteric modulatory activity of test compounds was performed as follows. Test compounds and glutamate were diluted in assay buffer containing 10 mM HEPES acid, 10 mM HEPES salt, pH 7.4, 100 mM NaCl, 3 mM MgCl₂ and 10 μM GDP. Human mGlu2 receptor-containing membranes were thawed on ice and diluted in assay buffer supplemented with 14 μg/ml saponin. Membranes were pre-incubated with compound alone or together with a predefined (˜EC₂₀) concentration of glutamate (PAM assay) for 30 min at 30° C. After addition of [³⁵S]GTPγS (f.c. 0.1 nM), assay mixtures were shaken briefly and further incubated to allow [³⁵S]GTPγS incorporation on activation (30 minutes, 30° C.). Final assay mixtures contained 7 μg of membrane protein in 10 mM HEPES acid, 10 mM HEPES salt, pH 7.4, 100 mM NaCl, 3 mM MgCl₂, 10 μM GDP and 10 μg/ml saponin. Total reaction volume was 200 μl. Reactions were terminated by rapid filtration through Unifilter-96 GF/B plates (Perkin Elmer, Massachusetts, USA) using a 96-well filtermate universal harvester. Filters were washed 6 times with ice-cold 10 mM NaH₂PO₄/10 mM Na₂HPO₄, pH 7.4. Filters were then air-dried, and 40 μl of liquid scintillation cocktail (Microscint-O) was added to each well. Membrane-bound radioactivity was counted in a Microplate Scintillation and Luminescence Counter from Perkin Elmer.

Data Analysis

The concentration-response curves of representative compounds of the present invention—obtained in the presence of EC₂₀ of mGluR2 agonist glutamate to determine positive allosteric modulation (PAM)—were generated using the Lexis software interface (developed at J&J). Data were calculated as % of the control glutamate response, defined as the maximal response that is generated upon addition of glutamate alone. Sigmoid concentration-response curves plotting these percentages versus the log concentration of the test compound were analyzed using non-linear regression analysis. The concentration producing half-maximal effect is then calculated as EC₅₀.

The pEC₅₀ values below were calculated as the −log EC₅₀, when the EC₅₀ is expressed in M. E_(max) is defined as relative maximal effect (i.e. maximal % effect relative to the control glutamate response).

Table 3 below shows the pharmacological data obtained for compounds of Formula (I).

TABLE 3 Pharmacological data for compounds according to the invention. GTPγS - GTPγS - hmGluR2 PAM hmGluR2 PAM Co No. pEC₅₀ E_(max) 1  6.77 238 2  6.37 136 4a 6.74 108 4b 6.71  52 5a 6.7  101 5b 6.86 126

All compounds were tested in presence of mGluR2 agonist glutamate at a predetermined EC₂₀ concentration, to determine positive allosteric modulation. pEC₅₀ values were calculated from a concentration-response experiment of at least 8 concentrations. If more experiments were performed, the average pEC₅₀ value is reported and error deviation was <0.5.

E. Prophetic Composition Examples

“Active ingredient” as used throughout these examples relates to a final compound of formula (I), the pharmaceutically acceptable salts thereof, the solvates and the stereochemically isomeric forms thereof.

Typical Examples of Recipes for the Formulation of the Invention are as Follows:

1. Tablets

Active ingredient 5 to 50 mg Di-calcium phosphate 20 mg Lactose 30 mg Talcum 10 mg Magnesium stearate 5 mg Potato starch ad 200 mg

In this Example, active ingredient can be replaced with the same amount of any of the compounds according to the present invention, in particular by the same amount of any of the exemplified compounds.

2. Suspension

An aqueous suspension is prepared for oral administration so that each 1 milliliter contains 1 to 5 mg of one of the active compounds, 50 mg of sodium carboxymethyl cellulose, 1 mg of sodium benzoate, 500 mg of sorbitol and water ad 1 ml.

3. Injectable

A parenteral composition is prepared by stirring 1.5% by weight of active ingredient of the invention in 10% by volume propylene glycol in water.

4. Ointment

Active ingredient 5 to 1000 mg Stearyl alcohol 3 g Lanoline 5 g White petroleum 15 g Water ad 100 g

In this Example, active ingredient can be replaced with the same amount of any of the compounds according to the present invention, in particular by the same amount of any of the exemplified compounds.

Reasonable variations are not to be regarded as a departure from the scope of the invention. It will be obvious that the thus described invention may be varied in many ways by those skilled in the art. 

The invention claimed is:
 1. A compound of formula (I)

or a stereoisomerically isomeric form thereof, wherein R¹ is selected from the group consisting of C₁₋₆alkyl, (C₃₋₈cycloalkyl)C₁₋₃alkyl, (C₁₋₃alkyloxy)C₁₋₃alkyl and C₁₋₃alkyl substituted with 1, 2 or 3 fluoro substituents; R² is selected from the group consisting of CI, CF₃, —CN and cyclopropyl; R³ is selected from the group consisting of hydrogen, methyl and CF₃; R⁴ is selected from the group consisting of hydrogen and methyl; or R³ and R⁴ together with the carbon to which they are bound form a cyclopropyl ring or a carbonyl group; L is selected from the group consisting of (L-c), (L-a), (L-b), (L-d), (L-e), (L-f) and (L-g):

wherein R^(5a), R^(5b), R^(5c) and R^(5d) are each independently selected from the group consisting of phenyl; phenyl substituted with 1 or 2 substituents each independently selected from the group consisting of C₁₋₃alkyloxy and halo; pyridinyl; pyridinyl substituted with 1 or 2 substituents each independently selected from the group consisting of C₁₋₃alkyl, C₁₋₃alkyloxy and halo; pyrimidinyl and pyrimidinyl substituted with 1 or 2 substituents each independently selected from the group consisting of C₁₋₃alkyl, C₁₋₃alkyloxy and halo; R^(5e) and R^(5f) are each independently selected from the group consisting of phenyl and phenyl substituted with 1 or 2 substituents each independently selected from the group consisting of C₁₋₃alkyloxy and halo; R^(5g) is selected from the group consisting of C₁₋₃alkyl, phenyl and phenyl optionally substituted with 1 or 2 substituents each independently selected from the group consisting of C₁₋₃alkyloxy and halo; R^(6a), R^(6b), R^(6c), R^(6e), R^(6f) and R^(6g) are each independently selected from the group consisting of hydrogen; fluoro; C₁₋₃alkyl; C₁₋₃alkyl substituted with 1, 2 or 3 fluoro substituents; C₁₋₃alkyloxy; C₁₋₃alkyloxy substituted with 1, 2 or 3 fluoro substituents; and C₃₋₆cycloalkyl; R^(7a), R^(8a), R^(7b), R^(8b), R^(7c), R^(8c), R^(7d), R^(8d), R^(7e), R^(8e), R^(7f) and R^(8f) are each independently selected from the group consisting of hydrogen, fluoro and methyl; R^(9b) is selected from the group consisting of hydrogen, C₁₋₃alkyl and C₃₋₆cycloalkyl; wherein each halo is selected from the group consisting of fluoro, chloro, bromo and iodo; or a pharmaceutically acceptable salt thereof.
 2. The compound according to claim 1, or a stereoisomeric form thereof, wherein R¹ is (cyclopropyl)methyl.
 3. The compound according to claim 1, wherein R² is CF₃.
 4. The compound according to claim 1, wherein R³ and R⁴ are both hydrogen.
 5. The compound according to claim 1, wherein L is (L-c), wherein R^(5c) is selected from phenyl optionally substituted with 1 or 2 fluoro substituents; R^(6c) is selected from hydrogen or methyl and R^(7c) and R^(8c) are both hydrogen.
 6. The compound according to claim 1, selected from the group consisting of 3-(cyclopropylmethyl)-7-[[(3R)-3-phenyl-4-morpholinyl]methyl]-8-(trifluoromethyl)-1,2,4-triazolo[4,3-a]pyridine, 3-(cyclopropylmethyl)-7-[[(3S)-3-phenyl-4-morpholinyl]methyl]-8-(trifluoromethyl)-1,2,4-triazolo[4,3-a]pyridine, 3-(cyclopropylmethyl)-7-{[(3*R)-3-(2-fluorophenyl)-3-methylmorpholin-4-yl]methyl}-8-(trifluoromethyl) [1,2,4]triazolo-[4,3-a]pyridine, 3-(cyclopropylmethyl)-7-{[(3*S)-3-(2-fluorophenyl)-3-methylmorpholin-4-yl]methyl}-8-(trifluoromethyl)[1,2,4]triazolo[4,3-a]pyridine, 3-(cyclopropylmethyl)-7-{[(3*R)-3-(2,4-difluorophenyl)-3-methylmorpholin-4-yl]methyl}-8-(trifluoromethyl)[1,2,4]triazolo[4,3-a]pyridine and 3-(cyclopropylmethyl)-7-{[(3*S)-3-(2,4-difluorophenyl)-3-methylmorpholin-4-yl]methyl}-8-(trifluoromethyl)[1,2,4]triazolo[4,3-a]pyridine, or a stereoisomeric form thereof, or a pharmaceutically acceptable salt thereof.
 7. A pharmaceutical composition comprising a therapeutically effective amount of a compound according to claim 1 and a pharmaceutically acceptable carrier or excipient.
 8. A pharmaceutical composition comprising (a) a compound as defined in claim 1; and (b) an mGluR2 orthosteric agonist.
 9. A process for preparing a pharmaceutical composition comprising a pharmaceutically acceptable carrier mixed with a therapeutically effective amount of a compound as defined in claim
 1. 10. A method for the treatment of a patient for a central nervous system disorder selected from the group schizophrenia, bipolar disorder (I and II), generalized anxiety disorder and migraine comprising administering a pharmaceutically acceptable amount of the compound of claim 1 to the patient.
 11. The method according to claim 10, wherein the central nervous system disorder is schizophrenia.
 12. The method according to claim 10 wherein the central nervous system disorder is generalised anxiety disorder.
 13. A method for the treatment of a patient for a central nervous system disorder selected from the group consisting of schizophrenia, bipolar disorder (I and II), generalized anxiety disorder and migraine comprising administering a pharmaceutically acceptable amount of the compound according to claim 1 in combination with a therapeutically effective amount of an orthosteric agonist of mGluR2 to the patient. 